U.S. patent application number 15/063842 was filed with the patent office on 2016-10-13 for unified structural and electrical interconnections for high temperature batteries.
The applicant listed for this patent is Ambri Inc.. Invention is credited to David J. Bradwell, Shazad Butt, Daniel M. Holzer, Michael J. McNeley, Zachary T. Modest, Hari P. Nayar, Donald R. Sadoway, Greg A. Thompson.
Application Number | 20160301038 15/063842 |
Document ID | / |
Family ID | 52689401 |
Filed Date | 2016-10-13 |
United States Patent
Application |
20160301038 |
Kind Code |
A1 |
Modest; Zachary T. ; et
al. |
October 13, 2016 |
UNIFIED STRUCTURAL AND ELECTRICAL INTERCONNECTIONS FOR HIGH
TEMPERATURE BATTERIES
Abstract
The present disclosure provides cell housings and cell packs
that are designed to serve both electrical and structural
functions. Cell housing side walls can be directly joined together
to create parallel connections within a module of cells. The series
connections can be formed by stacking one cell on top of another
cell, thus connecting the opposing polarity terminals of the two
cells. The cells can be designed to support the weight of the cells
above without the use of additional framework. This approach can
reduce tertiary interconnection mechanisms and/or the number of
components required to electrically connect and structurally
support cells, thus providing increased system efficiency and/or a
reduced system cost.
Inventors: |
Modest; Zachary T.; (Jamaica
Plain, MA) ; Holzer; Daniel M.; (Medford, MA)
; Nayar; Hari P.; (Woburn, MA) ; McNeley; Michael
J.; (Boston, MA) ; Thompson; Greg A.;
(Arlington, MA) ; Butt; Shazad; (Natick, MA)
; Bradwell; David J.; (Arlington, MA) ; Sadoway;
Donald R.; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ambri Inc. |
Cambridge |
MA |
US |
|
|
Family ID: |
52689401 |
Appl. No.: |
15/063842 |
Filed: |
March 8, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US2014/056367 |
Sep 18, 2014 |
|
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|
15063842 |
|
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61879349 |
Sep 18, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 2002/0297 20130101;
H01M 2220/20 20130101; H01M 4/381 20130101; Y02E 60/10 20130101;
H01M 2/1077 20130101; H01M 2/0285 20130101; H01M 4/38 20130101;
H01M 10/39 20130101; H01M 10/399 20130101; H01M 2/027 20130101;
H01M 2/206 20130101; H01M 4/387 20130101 |
International
Class: |
H01M 2/02 20060101
H01M002/02; H01M 4/38 20060101 H01M004/38; H01M 2/20 20060101
H01M002/20; H01M 10/39 20060101 H01M010/39; H01M 2/10 20060101
H01M002/10 |
Claims
1. A battery, comprising: a. a plurality of electrochemical cells
comprising a first cell and a second cell, each of the first cell
and the second cell comprising an electrically conductive housing
and a conductor in electrical communication with a current
collector, the electrically conductive housing comprising a
negative electrode, electrolyte and positive electrode, wherein at
least one of the negative electrode, electrolyte and positive
electrode is in a liquid state at an operating temperature of the
cell, wherein the conductor protrudes through the electrically
conductive housing through an aperture in the electrically
conductive housing and is electrically isolated from the
electrically conductive housing with a seal, and wherein the
plurality of electrochemical cells are stacked in series with the
conductor of the first cell in electrical contact with the
electrically conductive housing of the second cell; and b. a
plurality of non-gaseous spacers disposed between the
electrochemical cells.
2. (canceled)
3. The battery of claim 1, wherein the electrochemical cells are
stacked vertically.
4. The battery of claim 1, wherein a thickness of each of the
non-gaseous spacers is approximately equal to a distance that the
conductor protrudes through the electrically conductive
housing.
5.-20. (canceled)
21. The battery of claim 1, wherein the battery is capable of
storing at least about 10 kWh of energy.
22. The battery of claim 1, wherein the operating temperature is at
least about 250.degree. C.
23. The battery of claim 1, wherein the negative electrode
comprises an alkali or alkaline earth metal.
24. The battery of claim 23, wherein the alkali or alkaline earth
metal is lithium, sodium, potassium, magnesium, calcium, or any
combination thereof.
25.-26. (canceled)
27. The battery of claim 1, wherein the positive electrode
comprises one or more of tin, lead, bismuth, antimony, tellurium
and selenium.
28.-31. (canceled)
32. An electrochemical energy storage system, comprising at least a
first electrochemical cell adjacent to a second electrochemical
cell, each of the first and second electrochemical cells comprising
a negative current collector, negative electrode, electrolyte,
positive electrode and a positive currently collector, wherein at
least one of the negative electrode, electrolyte and positive
electrode is in a liquid state at an operating temperature of the
first or second electrochemical cell, and wherein the positive
current collector of the first electrochemical cell is in
electrical contact with the negative current collector of the
second electrochemical second cell via an electrical connection
that comprises a direct metal-to-metal joint.
33. The electrochemical energy storage system of claim 32, wherein
the direct metal-to-metal joint is formed of a braze or a weld.
34.-68. (canceled)
69. A battery comprising: a. at least a first electrochemical cell
adjacent to a second electrochemical cell, each of the first and
second electrochemical cells comprising a negative electrode,
electrolyte and positive electrode, wherein at least one of the
negative electrode, electrolyte and positive electrode is in a
liquid state at an operating temperature of a respective one of the
first and second electrochemical cells; and b. an interconnect or
busbar that electrically connects the first and second
electrochemical cells, wherein the interconnect or busbar comprises
a strain-relieving feature, and wherein the interconnect or busbar
comprises a conductive material.
70. (canceled)
71. The battery of claim 69, wherein the conductive material
comprises an aluminum-copper alloy.
72. The battery of claim 71, wherein the aluminum-copper alloy has
an electrical conductivity at an operating temperature of the
battery of at least about 2.times.10.sup.6 S/m.
73.-74. (canceled)
75. The battery of claim 69, wherein the conductive material
comprises an alloy of at least about 1 weight-percent aluminum with
copper, bronze or brass.
76. (canceled)
77. The battery of claim 69, wherein the conductive material
comprises stainless steel, nickel or a non-ferrous alloy.
78.-88. (canceled)
89. The battery of claim 69, wherein at least one of the first and
second electrochemical cells is part of a first plurality of
electrochemical cells connected in parallel, wherein the busbar is
in electrical communication with the first plurality of
electrochemical cells, and wherein an internal resistance between
the first plurality of electrochemical cells and a second plurality
of electrochemical cells connected to the busbar of the first
plurality of electrochemical cells is less than about 10
milliohm.
90. The battery of claim 69, wherein the negative electrode is
liquid at the operating temperature of a respective one of the
first electrochemical cell and the second electrochemical cell, and
wherein the negative electrode comprises (i) one or more alkali
metals, (ii) one or more alkaline earth metals, or (iii) lithium,
sodium, potassium, magnesium, calcium, or any combination
thereof.
91. The battery of claim 69, wherein the strain-relieving feature
has a spiral pattern.
92. The electrochemical energy storage system of claim 32, wherein
at least two of the negative electrode, electrolyte and positive
electrode are in a liquid state at the operating temperature.
93. The electrochemical energy storage system of claim 32, further
comprising a current transfer plate welded to the negative current
collector of the first electrochemical cell and the positive
current collector of the second electrochemical cell.
Description
CROSS-REFERENCE
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/879,349, filed Sep. 18, 2013, which is entirely
incorporated herein by reference.
BACKGROUND
[0002] A battery is a device capable of converting chemical energy
into electrical energy. Batteries are used in many household and
industrial applications. In some instances, batteries are
rechargeable such that electrical energy, which may be converted
from non-electrical energy (e.g., mechanical energy), is capable of
being stored in the battery as chemical energy.
SUMMARY
[0003] A liquid metal energy storage device (or battery) can
include a negative electrode, electrolyte and positive electrode,
at least some of which may be in the liquid state during operation
of the energy storage device. The battery is generally made up of a
number of (electrochemical) cells. Most batteries use the cell
housing as electrically insulating material.
[0004] The disclosure provides cell housings and cell packs that
are designed to serve both electrical and structural functions.
Cell housing side walls can be directly joined together to create
parallel connections within a module of cells. The series
connections can be formed by stacking one cell on top of another
cell, thus connecting the opposing polarity terminals of the two
cells. The cells can be designed to support the weight of the cells
above without the use of significant additional framework. This
approach can reduce tertiary interconnection mechanisms and/or the
number of components required to electrically connect and
structurally support cells, thus providing increased system
efficiency and/or a reduced system cost.
[0005] An aspect of the disclosure relates to a liquid metal
battery, comprising: (a) a plurality of electrochemical cells each
comprising an electrically conductive housing and a conductor in
electrical communication with a current collector, the electrically
conductive housing comprising a negative electrode, electrolyte and
positive electrode, wherein at least one of the negative electrode,
electrolyte and positive electrode are in a liquid state at an
operating temperature of the cell, wherein the conductor protrudes
through the electrically conductive housing through an aperture in
the electrically conductive housing and is electrically isolated
from the electrically conductive housing with a seal, and wherein
the plurality of electrochemical cells are stacked in series with
the conductor of a first cell in electrical contact with the
electrically conductive housing of a second cell; and (b) a
plurality of non-gaseous spacers disposed between the
electrochemical cells. At least 3 electrochemical cells can be
stacked in series. The electrochemical cells can be stacked
vertically. A thickness of each spacer can be approximately equal
to a distance that the conductor protrudes through the electrically
conductive housing. A displacement between the negative electrode
and the positive electrode can be determined by the non-gaseous
spacers. A force applied to the seal can be less than about 45
Newtons. At least 90% of a force applied to the first cell can be
applied to the non-gaseous spacers and/or the electrically
conductive housing of the first cell. The spacers can be
electrically insulating. The the spacers can comprise a ceramic
material. The conductor of the first cell can be brazed to the
electrically conductive housing of the second cell. The conductor
of the first cell can sit in a recessed portion of the electrically
conductive housing of the second cell, wherein a coefficient of
thermal expansion (CTE) of the conductor can be greater than a CTE
of the electrically conductive housing. In some cases, the
electrochemical cells that are connected in series are not
connected by wires. The electrically conductive housings can be
part of a current conducting pathway. The resistance of each
cell-to-cell series connection can be less than about 100 mOhm. The
resistance can be measured by a direct electrical connection
between the conductor of the first electrochemical cell and the
electrically conducting housing of the second cell. In some cases,
the battery further comprises at least one additional
electrochemical cell connected in parallel to each of the plurality
of electrochemical cells that are stacked in series. The parallel
connections can be made by creating the electrically conductive
housing for multiple cells from one manufactured part. The parallel
connections can be formed by interconnects that allow at least some
of the electrochemical cells comprising the battery to be replaced
without breaking a direct metal-to-metal joint. The parallel
connections can be formed by welding together features in cell
bodies of adjacent cells. In some cases, the battery comprises one
interconnect for at least every four electrochemical cells. The
battery can be capable of storing at least about 10 kWh of energy.
The operating temperature can be at least about 250.degree. C. In
some cases, the negative electrode comprises an alkali or alkaline
earth metal. The alkali or alkaline earth metal can be lithium,
sodium, potassium, magnesium, calcium, or any combination thereof.
In some cases, the positive electrodes comprises a Group 12
element. The Group 12 element can be zinc, cadmium or mercury. In
some cases, the positive electrode further comprises one or more of
tin, lead, bismuth, antimony, tellurium and selenium. In some
cases, the electrolyte comprises a salt of an alkali or alkaline
earth metal. In some cases, each cell operates at a charge cutoff
voltage of at least about 1.0 V after at least about 300
charge/discharge cycles. In some cases, each cell operates at a
charge cutoff voltage of at least about 1.7 V after at least about
100 charge/discharge cycles. In some cases, the battery further
comprises a current transfer plate welded to the conductor of the
first cell and the electrically conductive housing of the second
cell.
[0006] Another aspect of the disclosure is directed to an
electrochemical energy storage system, comprising at least a first
electrochemical cell adjacent to a second electrochemical cell,
each of the first and second electrochemical cells comprising a
negative current collector, negative electrode, electrolyte,
positive electrode and a positive currently collector, wherein at
least one of the negative electrode, electrolyte and positive
electrode is in a liquid state at an operating temperature of the
first or second electrochemical cell, and wherein the positive
current collector of the first electrochemical cell is direct
metal-to-metal joined to the negative current collector of the
second electrochemical second cell. The positive current collector
of the first electrochemical cell can be direct metal-to-metal
joined to the negative current collector of the second
electrochemical second cell by a braze or a weld. In some cases,
the first and second electrochemical cells are not connected by
wires. The electrochemical energy storage system can be capable of
storing at least about 10 kWh of energy. The electrochemical energy
storage system can operate at a temperature of at least about
250.degree. C. In some cases, the negative electrode comprises an
alkali or alkaline earth metal. The alkali or alkaline earth metal
can be lithium, sodium, potassium, magnesium, calcium, or any
combination thereof. In some cases, the positive electrode
comprises a Group 12 element. The Group 12 element can be zinc,
cadmium or mercury. In some cases, the positive electrode further
comprises one or more of tin, lead, bismuth, antimony, tellurium
and selenium. In some cases, the electrolyte comprises a salt of an
alkali or alkaline earth metal. In some cases, each cell operates
at a charge cutoff voltage of at least about 1.0 V after at least
about 300 charge/discharge cycles. In some cases, each cell
operates at a charge cutoff voltage of at least about 1.7 V after
at least about 100 charge/discharge cycles.
[0007] Another aspect of the disclosure relates to a battery
comprising electrochemical cells connected in series, the battery
comprising a plurality of modules each comprising electrochemical
cells in a parallel configuration, wherein the battery is capable
of storing at least about 10 kWh of energy, the battery has an
operating temperature of at least about 250.degree. C. and each of
the electrochemical cells has at least one liquid metal electrode,
wherein an internal resistance of the battery at the operating
temperature is less than about 1.50*n*R, where `n` is the number of
modules in the battery and `R` is the resistance of each of the
modules. n can be at least 3. In some cases, the internal
resistance of the battery at the operating temperature is less than
about 1.25*n*R. In some cases, the internal resistance of the
battery at the operating temperature is less than about 1.05*n*R.
In some cases, the battery comprises electrochemical cells
connected in series and in parallel. In some cases, the liquid
metal electrode comprises one or more Group 12 elements. The Group
12 elements can be zinc, cadmium or mercury. In some cases, the
liquid metal electrode further comprises one or more of tin, lead,
bismuth, antimony, tellurium and selenium. In some cases, the
liquid metal electrode comprises one or more alkali metals. In some
cases, the liquid metal electrode comprises one or more alkaline
earth metals. In some cases, the liquid metal electrode comprises
lithium, sodium, potassium, magnesium, calcium, or any combination
thereof. In some cases, the electrochemical cells are not connected
with wires. In some cases, the battery is capable of storing at
least about 10 kWh of energy. In some cases, the battery is capable
of storing at least about 100 kWh of energy.
[0008] A further aspect of the disclosure relates to a liquid metal
battery comprising: (a) a plurality of electrochemical cells
connected in series and parallel, wherein each of the
electrochemical cells comprises a negative electrode, electrolyte
and positive electrode, wherein at least one of the negative
electrode, electrolyte and positive electrode is in a liquid state
at an operating temperature of the electrochemical cell; (b) a
plurality of wires each having a first end and a second end; and
(c) a common single point connector in electrical communication
with at least one of the electrochemical cells, wherein each of the
first ends of the wires is connected to the common single point
connector. The single point connector can be connected to a busbar
that is in electrical communication with the at least one of the
electrochemical cells, a cell body that is in electrical
communication with the at least one of the electrochemical cells or
a feature in the cell body that is in electrical communication with
the at least one of the electrochemical cells. The feature in the
cell body can be a tab protruding from the cell body. At least one
of the second ends of the wires can be connected to control
circuitry. The at least one of the second ends of the wires can be
connected to a battery management system. At least one of the
second ends of the wires can be connected to another common single
point connector. The common single point connector can form an
electrical connection with another plurality of electrochemical
cells. At least 3 wires can be connected to the single point
connector. In some cases, the single point connector comprises a
bent nickel piece. The first ends of the wires can be passed
through holes in the bent nickel piece and/or welded to the bent
nickel piece.
[0009] A further aspect of the disclosure is directed to a liquid
metal battery comprising: (a) a first plurality of electrochemical
cells connected in parallel, wherein each of the electrochemical
cells comprises a negative electrode, electrolyte and positive
electrode, wherein at least one of the negative electrode,
electrolyte and positive electrode is in a liquid state at an
operating temperature of the electrochemical cell; and (b) a busbar
in electrical communication with the first plurality of
electrochemical cells, wherein the busbar comprises a conductive
material. The conductive material can comprise copper, and the
liquid metal battery can operate at a temperature of less than
about 450.degree. C. In some cases, the conductive material
comprises an aluminum-copper alloy. The aluminum-copper alloy can
have an electrical conductivity at an operating temperature of the
liquid metal battery of at least about 2.times.10.sup.6 S/m. The
aluminum-copper alloy can be coated with an oxidation-resistant
material. The oxidation-resistant material can be aluminum,
aluminum-bronze, aluminum-brass, chromium, nickel, stainless steel,
or any combination thereof. In some cases, the conductive material
comprises an alloy of at least about 1 weight-percent aluminum with
copper, bronze or brass. The conductive material can have an
electrical conductivity greater than about 2.times.10.sup.6 S/m at
20.degree. C. or greater than about 1.times.10.sup.6 S/m at
500.degree. C. In some cases, the conductive material comprises
stainless steel. In some cases, the conductive material comprises
nickel. In some cases, the conductive material is a non-ferrous
alloy. The busbar can be joined to a stainless steel end-cap. The
busbar can be brazed, press-fit or welded to a stainless steel
end-cap. Compared to the conductive material, the end-cap can be
more easily welded to another busbar, an interconnect or an
electrochemical cell. In some cases, the first plurality of
electrochemical cells further comprises electrochemical cells
connected in series. In some cases, the first plurality of
electrochemical cells comprises a parallel string of packs. The
busbar can be an interconnect. In some cases, the liquid metal
battery further comprises an interconnect that electrically
connects the busbar of the first plurality of electrochemical cells
with a second plurality of electrochemical cells, thereby placing
the first plurality and the second plurality in parallel or in
series. In some cases, the interconnect comprises the same
conductive material as the busbar. The operating temperature can be
at least about 250.degree. C. An internal resistance between the
first plurality of electrochemical cells and a second plurality of
electrochemical cells connected to the busbar of the first
plurality of electrochemical cells can be less than about 10
milliohm.
[0010] Additional aspects and advantages of the present disclosure
will become readily apparent to those skilled in this art from the
following detailed description, wherein only illustrative
embodiments of the present disclosure are shown and described. As
will be realized, the present disclosure is capable of other and
different embodiments, and its several details are capable of
modifications in various obvious respects, all without departing
from the disclosure. Accordingly, the drawings and description are
to be regarded as illustrative in nature, and not as
restrictive.
INCORPORATION BY REFERENCE
[0011] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent, or patent
application was specifically and individually indicated to be
incorporated by reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized, and the accompanying drawings or figures (also "FIG."
and "FIGs." herein), of which:
[0013] FIG. 1 is an illustration of an electrochemical cell (A) and
a compilation (i.e., battery) of electrochemical cells (B and
C);
[0014] FIG. 2 is a schematic cross-sectional illustration of a
housing having a conductor in electrical communication with a
current collector passing through an aperture in the housing;
[0015] FIG. 3 is a cross-sectional side view of an electrochemical
cell or battery;
[0016] FIG. 4 is a cross-sectional side view of an electrochemical
cell or battery with an intermetallic layer;
[0017] FIG. 5 shows a system programmed or otherwise configured to
control or regulate one or more process parameters of an energy
storage system of the present disclosure;
[0018] FIG. 6 shows an example of a cell pack;
[0019] FIG. 7 shows an example of braze connection between the top
of a conductive feed-through and the bottom of a cell;
[0020] FIG. 8 shows an example of joining two cells using a
compression connection between parts that forms at the operating
temperature of the battery based on differences in the coefficient
of thermal expansion;
[0021] FIG. 9 shows an example of a stack of cell packs, also
referred to as a core;
[0022] FIG. 10 is an example of a busbar configuration;
[0023] FIG. 11 shows an example of a cell module with busbars and
wires;
[0024] FIG. 12 shows an example of a single point connector;
[0025] FIG. 13 is a perspective view of an electrochemical cell
with a current transfer plate 1310 attached to a negative current
lead; and
[0026] FIG. 14 is an example of a pack with a first interpack
busbar and a second interpack busbar.
DETAILED DESCRIPTION
[0027] While various embodiments of the invention have been shown
and described herein, it will be obvious to those skilled in the
art that such embodiments are provided by way of example only.
Numerous variations, changes, and substitutions may occur to those
skilled in the art without departing from the invention. It should
be understood that various alternatives to the embodiments of the
invention described herein may be employed. It shall be understood
that different aspects of the invention can be appreciated
individually, collectively, or in combination with each other.
[0028] The term "cell," as used herein, generally refers to an
electrochemical cell. A cell can include a negative electrode of
material `A` and a positive electrode of material `B`, denoted as
A.parallel.B. The positive and negative electrodes can be separated
by an electrolyte. A cell can also include a housing, one or more
current collectors, and a high temperature electrically isolating
seal. In some cases, a cell can be about 4 inches wide, about 4
inches deep and about 2.5 inches tall. In some cases, a cell can be
about 8 inches wide, about 8 inches deep and about 2.5 inches tall.
In some examples, any given dimension (e.g., height, width or
depth) of an electrochemical cell can be about 1, 2, 2.5, 3, 3.5,
4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 12, 14, 16, 18
or 20 inches. In one example, a cell (e.g., each cell) can have
dimensions of about 4 inches.times.4 inches.times.2.5 inches. In
another example, a cell (e.g., each cell) can have dimensions of
about 8 inches.times.8 inches.times.2.5 inches. In some cases, a
cell may have about 70 Watt-hours of energy storage capacity. In
some cases, a cell may have about 300 Watt-hours of energy storage
capacity.
[0029] The term "module," as used herein, generally refers to cells
that are attached together in parallel by, for example,
mechanically connecting the cell housing of one cell with the cell
housing of an adjacent cell (e.g., cells that are connected
together in an approximately horizontal packing plane). In some
cases, the cells are connected to each other by joining features
that are part of and/or connected to the cell body (e.g., tabs
protruding from the main portion of the cell body). A module can
include a plurality of cells in parallel. A module can comprise any
number of cells (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, or more). In some cases, a module comprises
4, 9, 12, or 16 cells. In some cases, a module is capable of
storing about 700 Watt-hours of energy and/or delivering about 175
Watts of power. In some cases, a module is capable of storing about
1080 Watt-hours of energy and/or delivering about 500 Watts of
power. In some cases, a module is capable of storing about 1080
Watt-hours of energy and/or delivering at least about 200 Watts
(e.g., about 500 Watts) of power. In some cases, a module can
include a single cell.
[0030] The term "pack," as used herein, generally refers to modules
that are attached through different electrical connections (e.g.,
vertically). A pack can comprise any number of modules (e.g., 1, 2,
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or
more). In some cases, a pack comprises 3 modules. In some cases, a
pack is capable of storing about 2 kilo-Watt-hours of energy and/or
delivering at least about 0.4 kilo-Watts (e.g., about 0.5
kilo-Watts or about 1.0 kilo-Watts) of power. In some cases, a pack
is capable of storing about 3 kilo-Watt-hours of energy and/or
delivering at least about 0.75 kilo-Watts (e.g., about 1.5
kilo-Watts) of power. In some cases, a pack comprises 6 modules. In
some cases, a pack is capable of storing about 6 kilo-Watt-hours of
energy and/or delivering at least about 1.5 kilo-Watts (e.g., about
3 kilo-Watts) of power.
[0031] The term "core," as used herein generally refers to a
plurality of modules or packs that are attached through different
electrical connections (e.g., in series and/or parallel). A core
can comprise any number of modules or packs (e.g., 1, 2, 3, 4, 5,
6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
or more). In some cases, the core also comprises mechanical,
electrical, and thermal systems that allow the core to efficiently
store and return electrical energy in a controlled manner. In some
cases, a core comprises 12 packs. In some cases, a core is capable
of storing about 25 kilo-Watt-hours of energy and/or delivering
about 6.25 kilo-Watts of power. In some cases, a core comprises 36
packs. In some cases, a core is capable of storing about 200
kilo-Watt-hours of energy and/or delivering at least about 40
kilo-Watts (e.g., at least or about 40, 50, 60, 70, 80, 90 or 100
kilo-Watts) of power.
[0032] The term "core enclosure", or "CE," as used herein,
generally refers to a plurality of cores that are attached through
different electrical connections (e.g., in series and/or parallel).
A CE can comprise any number of cores (e.g., 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more). In some
cases, the CE contains cores that are connected in parallel with
appropriate by-pass electronic circuitry, thus enabling a core to
be disconnected while continuing to allow the other cores to store
and return energy. In some cases, a CE comprises 4 cores. In some
cases, a CE is capable of storing about 100 kilo-Watt-hours of
energy and/or delivering about 25 kilo-Watts of power. In some
cases, a CE is capable of storing about 400 kilo-Watt-hours of
energy and/or delivering at least about 80 kilo-Watts (e.g., at
least or about 80, 100, 120, 140, 160, 180 or 200 kilo-Watts) of
power.
[0033] The term "system," as used herein, generally refers to a
plurality of cores or CEs that are attached through different
electrical connections (e.g., in series and/or parallel). A system
can comprise any number of cores or CEs (e.g., 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more). In some
cases, a system comprises 20 CEs. In some cases, a system is
capable of storing about 2 mega-Watt-hours of energy and/or
delivering at least about 400 kilo-Watts (e.g., about 500
kilo-Watts or about 1000 kilo-Watts) of power. In some cases, a
system comprises 5 CEs. In some cases, a system is capable of
storing about 2 mega-Watt-hours of energy and/or delivering at
least about 400 kilo-Watts (e.g., at least or about 400, 500, 600,
700, 800, 900 or 1000 kilo-Watts) of power.
[0034] A group of cells (e.g., a core, a CE, a system, etc.) with a
given energy capacity and power capacity (e.g., a CE or a system
capable of storing a given amount of energy) may be configured to
deliver at least about 10%, at least about 20%, at least about 30%,
at least about 40%, at least about 50%, at least about 60%, at
least about 70%, at least about 80%, at least about 90%, at least
about 95%, or about 100% of a given (e.g., rated) power level. For
example, a 1000 kW system may be capable of also operating at 500
kW, but a 500 kW system may not be able to operate at 1000 kW. In
some cases, a system with a given energy capacity and power
capacity (e.g., a CE or a system capable of storing a given amount
of energy) may be configured to deliver less than about 100%, less
than about 110%, less than about 125%, less than about 150%, less
than about 175%, or less than about 200% of a given (e.g., rated)
power level, and the like. For example, the system may be
configured to provide more than its rated power capacity for a
period of time that is less than the time it would take to consume
its energy capacity at the power level that is being provided
(e.g., provide power that is greater than the rated power of the
system for a period of time corresponding to less than about 1%,
less than about 10% or less than about 50% of its rated energy
capacity).
[0035] The term "battery," as used herein, generally refers to one
or more electrochemical cells connected in series and/or parallel.
A battery can comprise any number of electrochemical cells,
modules, packs, cores, CEs or systems.
[0036] The term "direct metal-to-metal joining" or "direct
metal-to-metal joint," as used herein, generally refers to an
electrical connection where two metal surfaces are brought into
contact (e.g., by forming a braze or a weld). In some examples,
direct metal-to-metal joints do not include wires.
[0037] The term "interconnect," as used herein, generally refers to
any electrical connection other than a direct metal-to-metal joint.
Interconnects can include wires or bent sheet metal components
designed to pass current. Interconnects may be compliant (e.g.,
flexible).
[0038] The term "wire," as used herein, generally refers to any
cord, strip, or elongated electrical conduit. Wires can be
flexible. As used herein, a braided metal strip is a wire. In some
cases, a busbar is a wire.
[0039] The term "vertical," as used herein, generally refers to a
direction that is parallel to the force of gravity.
[0040] The term "cycle," as used herein, generally refers to a
charge/discharge or discharge/charge cycle.
[0041] The term "charge cutoff voltage" or "CCV," as used herein,
generally refers to the voltage at which a cell is fully or
substantially fully charged, such as a voltage cutoff limit used in
a battery when cycled in a constant current mode.
[0042] The term "open circuit voltage" or "OCV," as used herein,
generally refers to the voltage of a cell (e.g., fully or partially
charged) when it is disconnected from any circuit or external load
(i.e., when no current is flowing through the cell).
[0043] The term "voltage" or "cell voltage," as used herein,
generally refers to the voltage of a cell (e.g., at any state of
charge or charging/discharging condition). In some cases, voltage
or cell voltage may be the open circuit voltage. In some cases, the
voltage or cell voltage can be the voltage during charging or
during discharging.
[0044] Voltages of the present disclosure may be taken or
represented with respect to reference voltages, such as ground (0
V).
[0045] Electrochemical Cells, Devices and Systems
[0046] The present disclosure provides electrochemical energy
storage devices (e.g., batteries) and systems. An electrochemical
energy storage device generally includes at least one
electrochemical cell, also "cell" and "battery cell" herein, sealed
(e.g., hermetically sealed) within a housing. A cell can be
configured to deliver electrical energy (e.g., electrons under
potential) to a load, such as, for example, an electronic device,
another energy storage device or a power grid.
[0047] An electrochemical cell of the disclosure can include a
negative electrode, an electrolyte adjacent to the negative
electrode, and a positive electrode adjacent to the electrolyte.
The negative electrode can be separated from the positive electrode
by the electrolyte. The negative electrode can be an anode during
discharge. The positive electrode can be a cathode during
discharge.
[0048] In some examples, an electrochemical cell is a liquid metal
battery cell. In some examples, a liquid metal battery cell can
include a liquid electrolyte arranged between a negative liquid
(e.g., molten) metal electrode and a positive liquid (e.g., molten)
metal, metalloid and/or non-metal electrode. In some cases, a
liquid metal battery cell has a molten alkaline earth metal (e.g.,
magnesium, calcium) or alkali metal (e.g., lithium, sodium,
potassium) negative electrode, an electrolyte, and a molten metal
positive electrode. The molten metal positive electrode can
include, for example, one or more of tin, lead, bismuth, antimony,
tellurium and selenium. For example, the positive electrode can
include Pb or a Pb--Sb alloy. The positive electrode can also
include one or more transition metals or d-block elements (e.g.,
Zn, Cd, Hg) alone or in combination with other metals, metalloids
or non-metals, such as, for example, a Zn--Sn alloy or Cd--Sn
alloy. Any description of a metal or molten metal positive
electrode, or a positive electrode, herein may refer to an
electrode including one or more of a metal, a metalloid and a
non-metal. The positive electrode may contain one or more of the
listed examples of materials. In an example, the molten metal
positive electrode can include lead and antimony. In some examples,
the molten metal positive electrode may include an alkali or
alkaline earth metal alloyed in the positive electrode.
[0049] In some examples, an electrochemical energy storage device
includes a liquid metal negative electrode, a liquid metal positive
electrode, and a liquid salt electrolyte separating the liquid
metal negative electrode and the liquid metal positive electrode.
The negative electrode can include an alkali or alkaline earth
metal, such as lithium, sodium, potassium, rubidium, cesium,
magnesium, barium, calcium, sodium, or combinations thereof. The
positive electrode can include elements selected from transition
metals or d-block elements (e.g., Group 12), Group IIIA, IVA, VA
and VIA of the periodic table of the elements, such as zinc,
cadmium, mercury, aluminum, gallium, indium, silicon, germanium,
tin, lead, pnicogens (e.g., arsenic, bismuth and antimony),
chalcogens (e.g., tellurium and selenium), or combinations thereof.
In some examples, the positive electrode comprises a Group 12
element of the periodic table of the elements, such as one or more
of zinc (Zn), cadmium (Cd) and mercury (Hg). In some cases, the
positive electrode may form a eutectic or off-eutectic mixture
(e.g., enabling lower operating temperature of the cell in some
cases). In some examples, the positive electrode comprises a first
positive electrode species and a second positive electrode species
at a ratio (mol %) of about 20:80, 40:60 or 80:20 of the first
positive electrode species to the second electrode species. In some
examples, the positive electrode comprises Sb and Pb at a ratio
(mol %) of about 20:80, 40:60 or 80:20 Sb to Pb. In some examples,
the positive electrode comprises between about 20 mol % and 80 mol
% of a first positive electrode species mixed with a second
positive electrode species. In some cases, the positive electrode
comprises between about 20 mol % and 80 mol % Sb (e.g., mixed with
Pb). In some cases, the positive electrode comprises between about
20 mol % and 80 mol % Pb (e.g., mixed with Sb).
[0050] The electrolyte can include a salt (e.g., molten salt), such
as an alkali or alkaline earth metal salt. The alkali or alkaline
earth metal salt can be a halide, such as a fluoride, chloride,
bromide, or iodide of the active alkali or alkaline earth metal, or
combinations thereof. In an example, the electrolyte (e.g., in Type
1 or Type 2 chemistries) includes lithium chloride. In some
examples, the electrolyte can comprise sodium fluoride (NaF),
sodium chloride (NaCl), sodium bromide (NaBr), sodium iodide (NaI),
lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide
LiBr, lithium iodide (LH), potassium fluoride (KF), potassium
chloride (KCl), potassium bromide (KBr), potassium iodide (KI),
calcium fluoride (CaF.sub.2), calcium chloride (CaCl.sub.2),
calcium bromide (CaBr.sub.2), calcium iodide (CaI.sub.2), or any
combination thereof. As an alternative, the salt of the active
alkali metal can be, for example, a non-chloride halide,
bistriflimide, fluorosulfano-amine, perchlorate,
hexaflourophosphate, tetrafluoroborate, carbonate, hydroxide,
nitrate, nitrite, sulfate, sulfite, or combinations thereof. In
some cases, the electrolyte can comprise a mixture of salts. The
electrolyte may exhibit low (e.g., minimal) electronic conductance
(e.g., electronic shorting may occur through the electrolyte via
valence reactions of PbCl.sub.2.revreaction.PbC1.sub.3 which
increases electronic conductance). For example, the electrolyte can
have an electronic transference number (i.e., percentage of
electrical (electronic and ionic) charge that is due to the
transfer of electrons) of less than or equal to about 0.03% or
0.3%.
[0051] In some cases, the negative electrode and the positive
electrode of an electrochemical energy storage device are in the
liquid state at an operating temperature of the energy storage
device. To maintain the electrodes in the liquid states, the
battery cell may be heated to any suitable temperature. In some
examples, the battery cell is heated to and/or maintained at a
temperature of about 100.degree. C., about 150.degree. C., about
200.degree. C., about 250.degree. C., about 300.degree. C., about
350.degree. C., about 400.degree. C., about 450.degree. C., about
500.degree. C., about 550.degree. C., about 600.degree. C., about
650.degree. C., or about 700.degree. C. The battery cell may be
heated to and/or maintained at a temperature of at least about
100.degree. C., at least about 150.degree. C., at least about
200.degree. C., at least about 250.degree. C., at least about
300.degree. C., at least about 350.degree. C., at least about
400.degree. C., at least about 450.degree. C., at least about
500.degree. C., at least about 550.degree. C., at least about
600.degree. C., at least about 650.degree. C., or at least about
700.degree. C. In some situations, the battery cell is heated to
between about 200.degree. C. and about 600.degree. C., or between
about 450.degree. C. and about 575.degree. C. In some
implementations, the electrochemical cell or energy storage device
may be at least partially or fully self-heated. For example, a
battery may be sufficiently insulated, charged, discharged and/or
conditioned at sufficient rates, and/or cycled a sufficient
percentage of the time to allow the system to generate sufficient
heat through inefficiencies of the cycling operation that cells are
maintained at a given operating temperature (e.g., a cell operating
temperature above the freezing point of at least one of the liquid
components) without the need for additional energy to be supplied
to the system to maintain the operating temperature.
[0052] Electrochemical cells of the disclosure may be adapted to
cycle between charged (or energy storage) modes and discharged
modes. In some examples, an electrochemical cell can be fully
charged, partially charged or partially discharged, or fully
discharged.
[0053] In some implementations, during a charging mode of an
electrochemical energy storage device, electrical current received
from an external power source (e.g., a generator or an electrical
grid) may cause metal atoms in the metal positive electrode to
release one or more electrons, dissolving into the electrolyte as a
positively charged ion (i.e., cation). Simultaneously, cations of
the same species can migrate through the electrolyte and may accept
electrons at the negative electrode, causing the cations to
transition to a neutral metal species, thereby adding to the mass
of the negative electrode. The removal of the active metal species
from the positive electrode and the addition of the active metal to
the negative electrode stores electrochemical energy. In some
cases, the removal of a metal from the positive electrode and the
addition of its cation to the electrolyte can store electrochemical
energy. In some cases, electrochemical energy can be stored through
a combination of removal of the active metal species from the
positive electrode and its addition to the negative electrode, and
the removal of one or more metals (e.g., different metals) from the
positive electrode and their addition to the electrolyte (e.g., as
cations). During an energy discharge mode, an electrical load is
coupled to the electrodes and the previously added metal species in
the negative electrode can be released from the metal negative
electrode, pass through the electrolyte as ions, and deposit as a
neutral species in the positive electrode (and in some cases alloy
with the positive electrode material), with the flow of ions
accompanied by the external and matching flow of electrons through
the external circuit/load. In some cases, one or more cations of
positive electrode material previously released into the
electrolyte can deposit as neutral species in the positive
electrode (and in some cases alloy with the positive electrode
material), with the flow of ions accompanied by the external and
matching flow of electrons through the external circuit/load. This
electrochemically facilitated metal alloying reaction discharges
the previously stored electrochemical energy to the electrical
load.
[0054] In a charged state, the negative electrode can include
negative electrode material and the positive electrode can include
positive electrode material. During discharging (e.g., when the
battery is coupled to a load), the negative electrode material
yields one or more electrons, and cations of the negative electrode
material. In some implementations, the cations migrate through the
electrolyte to the positive electrode material and react with the
positive electrode material (e.g., to form an alloy). In some
implementations, ions of the positive metal species (e.g., cations
of the positive electrode material) accept electrons at the
positive electrode and deposit as a metal on the positive
electrode. During charging, in some implementations, the alloy at
the positive electrode disassociates to yield cations of the
negative electrode material, which migrate through the electrolyte
to the negative electrode. In some implementations, one or more
metal species at the positive electrode disassociates to yield
cations of the negative electrode material in the electrolyte. In
some examples, ions can migrate through an electrolyte from an
anode to a cathode, or vice versa. In some cases, ions can migrate
through an electrolyte in a push-pop fashion in which an entering
ion of one type ejects an ion of the same type from the
electrolyte. For example, during discharge, an alkali metal anode
and an alkali metal chloride electrolyte can contribute an alkali
metal cation to a cathode by a process in which an alkali metal
cation formed at the anode interacts with the electrolyte to eject
an alkali metal cation from the electrolyte into the cathode. The
alkali metal cation formed at the anode in such a case may not
necessarily migrate through the electrolyte to the cathode. The
cation can be formed at an interface between the anode and the
electrolyte, and accepted at an interface of the cathode and the
electrolyte.
[0055] The present disclosure provides Type 1 and Type 2 cells,
which can vary based on, and be defined by, the composition of the
active components (e.g., negative electrode, electrolyte and
positive electrode), and based on the mode of operation of the
cells (e.g., low voltage mode versus high voltage mode).
[0056] Electrochemical cells of the disclosure can include housings
that may be suited for various uses and operations. A housing can
include one cell or a plurality of cells. A housing can be
configured to electrically couple the electrodes to a switch, which
can be connected to the external power source and the electrical
load. The cell housing may include, for example, an electrically
conductive container that is electrically coupled to a first pole
of the switch and/or another cell housing, and an electrically
conductive container lid that is electrically coupled to a second
pole of the switch and/or another cell housing. The cell can be
arranged within a cavity of the container. A first one of the
electrodes of the cell can contact and be electrically coupled with
an endwall of the container. An electrically insulating seal (e.g.,
bonded ceramic ring) may electrically isolate negative potential
portions of the cell from positive portions of the container (e.g.,
electrically insulate the negative current lead from the positive
current lead). In an example, the negative current lead and the
container lid (e.g., cell cap) can be electrically isolated from
each other, where a dielectric sealant material can be placed
between the negative current lead and the cell cap. As an
alternative, a housing includes an electrically insulating sheath
(e.g., alumina sheath) or corrosion resistant and electrically
conductive sheath or crucible (e.g., graphite sheath or crucible).
In some cases, a housing and/or container may be a battery housing
and/or container.
[0057] A battery, as used herein, can comprise a plurality of
electrochemical cells. Individual cells can be electrically coupled
to one another in series and/or in parallel. In series
connectivity, the positive terminal of a first cell is connected to
a negative terminal of a second cell. In parallel connectivity, the
positive terminal of a first cell can be connected to a positive
terminal of a second, and/or additional, cell(s). Similarly, cell
modules, packs, cores, CEs and systems can be connected in series
and/or in parallel in the same manner as described for cells.
[0058] Reference will now be made to the figures, wherein like
numerals refer to like parts throughout. It will be appreciated
that the figures and features therein are not necessarily drawn to
scale.
[0059] With reference to FIG. 1, an electrochemical cell (A) is a
unit comprising an anode and a cathode. The cell may comprise an
electrolyte and be sealed in a housing as described herein. In some
cases, the electrochemical cells can be stacked (B) to form a
battery (i.e., a compilation of one or more electrochemical cells).
The cells can be arranged in parallel, in series, or both in
parallel and in series (C).
[0060] Further, as described in greater detail elsewhere herein,
the cells can be arranged in groups (e.g., modules, packs, cores,
CEs, systems, or any other group comprising one or more
electrochemical cells). In some cases, such groups of
electrochemical cells may allow a given number of cells to be
controlled or regulated together at the group level (e.g., in
concert with or instead of regulation/control of individual
cells).
[0061] The battery may be assembled through repeated addition of
individual cells or groups of cells. In one example, cells can be
assembled into modules, which can be stacked to form packs, which
can then be interconnected to form cores. In some cases, the packs
may be assembled (e.g., vertically and/or horizontally) on trays,
which is another example of a group of electrochemical cells; the
trays can be assembled (e.g., vertically and/or horizontally) to
form cores. Further, the cores can then be interconnected to form
CEs and systems. In another example, cells can be assembled into
modules, which can be interconnected (e.g., vertically and
horizontally) to form cores. In yet another example, cells can be
stacked to form a single cell tower (see, for example, FIG. 1B),
which is yet another example of a group of electrochemical cells.
Multiple cell towers, each comprising multiple cells stacked
vertically on top one another, can then be added together to form,
for example, a pack. Thus, in an example, a pack comprising a stack
of 4 modules, each module comprising a 2 by 2 array of cells, can
also be assembled by interconnecting 4 towers with 4 cells each
(arranged in a 2 by 2 array of towers). Groups of cells utilized
for assembly purposes may or may not be the same as groups of cells
utilized for regulation/control purposes.
[0062] Cells, cell modules, packs, cores, CEs and/or systems can be
connected in series and/or in parallel. Described throughout the
disclosure are various configurations in which cells or groups of
cells can be interconnected. Given the modular nature of the
assembly process, interconnection configurations described herein
in relation to individual cells or a given group of cells may
equally apply to other groups of cells at least in some
configurations.
[0063] Electrochemical cells of the disclosure may be capable of
storing and/or receiving input of ("taking in") substantially large
amounts of energy. In some instances, a cell is capable of storing
and/or taking in and/or discharging about 1 watt-hour (Wh), about 5
Wh, 25 Wh, about 50 Wh, about 100 Wh, about 250 Wh, about 500 Wh,
about 1 kilo-Watt-hour (kWh), about 1.5 kWh, or about 2 kWh. In
some instances, the battery is capable of storing and/or taking in
at least about 1 Wh, at least about 5 Wh, at least about 25 Wh, at
least about 50 Wh, at least about 100 Wh, at least about 250 Wh, at
least about 500 Wh, at least about 1 kWh, at least about 1.5 kWh,
at least about 2 kWh, at least about 3 kWh, at least about 5 kWh,
at least about 10 kWh, at least about 15 kWh, at least about 20
kWh, at least about 30 kWh, at least about 40 kWh, or at least
about 50 kWh. It is recognized that the amount of energy stored in
an electrochemical cell and/or battery may be less than the amount
of energy taken into the electrochemical cell and/or battery (e.g.,
due to inefficiencies and losses).
[0064] A cell can be capable of providing a current at a current
density of at least about 10 milliamperes per square centimeter
(mA/cm.sup.2), 20 mA/cm.sup.2, 30 mA/cm.sup.2, 40 mA/cm.sup.2, 50
mA/cm.sup.2, 60 mA/cm.sup.2, 70 mA/cm.sup.2, 80 mA/cm.sup.2, 90
mA/cm.sup.2, 100 mA/cm.sup.2, 200 mA/cm.sup.2, 300 mA/cm.sup.2, 400
mA/cm.sup.2, 500 mA/cm.sup.2, 600 mA/cm.sup.2, 700 mA/cm.sup.2, 800
mA/cm.sup.2, 900 mA/cm.sup.2, 1 A/cm.sup.2, 2 A/cm.sup.2, 3
A/cm.sup.2, 4 A/cm.sup.2, 5 A/cm.sup.2, or 10 A/cm.sup.2, where the
current density is determined based on the effective
cross-sectional area of the electrolyte and where the
cross-sectional area is the area that is orthogonal to the net flow
direction of ions through the electrolyte during charge or
discharging processes. In some instances, a cell can be capable of
operating at a direct current (DC) efficiency of at least about
10%, 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,
90%, 95% and the like. In some instances, a cell can be capable of
operating at a charge efficiency (e.g., Coulombic charge
efficiency) of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%,
80%, 85%, 90%, 95%, 98%, 99%, 99.5%, 99.9%, 99.95%, and the
like.
[0065] An electrochemical cell of the present disclosure can have a
response time of any suitable value (e.g., suitable for responding
to disturbances in the power grid). In some instances, the response
time is about 100 milliseconds (ms), about 50 ms, about 10 ms,
about 1 ms, and the like. In some cases, the response time is at
most about 100 milliseconds (ms), at most about 50 ms, at most
about 10 ms, at most about 1 ms, and the like.
[0066] A compilation or array of cells (e.g., battery) can include
any suitable number of cells, such as at least about 2, at least
about 5, at least about 10, at least about 50, at least about 100,
at least about 500, at least about 1000, at least about 5000, at
least about 10000, and the like. In some examples, a battery
includes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70,
80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000,
5000, 10,000, 20,000, 50,000, 100,000, 500,000, or 1,000,000
cells.
[0067] Batteries of the disclosure may be capable of storing and/or
taking in a substantially large amount of energy for use with a
power grid (i.e., a grid-scale battery) or other loads or uses. In
some instances, a battery is capable of storing and/or taking in
and/or discharging about 5 kilo-Watt-hour (kWh), about 25 kWh,
about 50 kWh, about 100 kWh, about 500 kWh, about 1 mega-Watt-hour
(MWh), about 1.5 MWh, about 2 MWh, about 3 MWh, about 5 MWh, about
10 MWh, about 25 MWh, about 50 MWh, or about 100 MWh. In some
instances, the battery is capable of storing and/or taking in at
least about 1 kWh, at least about 5 kWh, at least about 25 kWh, at
least about 50 kWh, at least about 100 kWh, at least about 500 kWh,
at least about 1 MWh, at least about 1.5 MWh, at least about 2 MWh,
at least about 3 MWh, at least about 4 MWh, at least about 5 MWh,
at least about 10 MWh, at least about 25 MWh, at least about 50
MWh, or at least about 100 MWh.
[0068] In some instances, the cells and cell housings are
stackable. Any suitable number of cells can be stacked. Cells can
be stacked side-by-side, on top of each other, or both. In some
instances, at least about 3, 6, 10, 50, 100, or 500 cells are
stacked. In some cases, a stack of 100 cells is capable of storing
and/or taking in at least 50 kWh of energy. A first stack of cells
(e.g., 10 cells) can be electrically connected to a second stack of
cells (e.g., another 10 cells) to increase the number of cells in
electrical communication (e.g., 20 in this instance). In some
instances, the energy storage device comprises a stack of 1 to 10,
11 to 50, 51 to 100, or more electrochemical cells.
[0069] An electrochemical energy storage device can include one or
more individual electrochemical cells. An electrochemical cell can
be housed in a container, which can include a container lid (e.g.,
cell cap) and seal component. The device can include at least 1, 2,
3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 100, 200, 300, 400, 500,
1000, 10,000, 100,000 or 1,000,000 cells. The container lid may
utilize, for example, a seal (e.g., annular dielectric gasket) to
electrically isolate the container from the container lid. Such a
component may be constructed from an electrically insulating
material, such as, for example, glass, oxide ceramics, nitride
ceramics, chalcogenides, or a combination thereof (e.g., ceramic,
silicon oxide, aluminum oxide, nitrides comprising boron nitride,
aluminum nitride, zirconium nitride, titanium nitride, carbides
comprising silicon carbide, titanium carbide, or other oxides
comprising of lithium oxide, calcium oxide, barium oxide, yttrium
oxide, silicon oxide, aluminum oxide, or lithium nitride, or any
combinations thereof). The seal may be made hermetic by one or more
methods. For example, the seal may be subject to relatively high
compressive forces (e.g., greater than about 1,000 psi or greater
than about 10,000 psi) between the container lid and the container
in order to provide a seal in addition to electrical isolation.
Alternatively, the seal may be bonded through a weld, a braze, or
other chemically adhesive material that joins relevant cell
components to the insulating sealant material.
[0070] FIG. 2 schematically illustrates a battery that comprises an
electrically conductive housing 201 and a conductor 202 in
electrical communication with a current collector 203. The battery
of FIG. 2 can be a cell of an energy storage device. The conductor
can be electrically isolated from the housing and can protrude
through the housing through an aperture in the housing such that
the conductor of a first cell is in electrical communication with
the housing of a second cell when the first and second cells are
stacked.
[0071] In some cases, a cell comprises a negative current
collector, a negative electrode, an electrolyte, a positive
electrode and a positive current collector. The negative electrode
can be part of the negative current collector. As an alternative,
the negative electrode is separate from, but otherwise kept in
electrical communication with, the negative current collector. The
positive electrode can be part of the positive current collector.
As an alternative, the positive electrode can be separate from, but
otherwise kept in electrical communication with, the positive
current collector.
[0072] A cell housing can comprise an electrically conductive
container and a conductor in electrical communication with a
current collector. The conductor may protrude through the housing
through an aperture in the container and may be electrically
isolated from the container. The conductor of a first housing may
contact the container of a second housing when the first and second
housings are stacked.
[0073] In some instances, the area of the aperture through which
the conductor protrudes from the housing and/or container is small
relative to the area of the housing and/or container. In some
cases, the ratio of the area of the aperture to the area of the
housing is about 0.001, about 0.005, about 0.01, about 0.05, about
0.1, about 0.15, or about 0.2. In some cases, the ratio of the area
of the aperture to the area of the housing is less than or equal to
0.001, less than or equal to 0.005, less than or equal to 0.01,
less than or equal to 0.05, less than or equal to 0.1, less than or
equal to 0.15, less than or equal to 0.2, or less than or equal to
0.3.
[0074] A cell can comprise an electrically conductive housing and a
conductor in electrical communication with a current collector. The
conductor protrudes through the housing through an aperture in the
housing and may be electrically isolated from the housing. The
ratio of the area of the aperture to the area of the housing may be
less than about 0.3, 0.2, 0.15, 0.1, 0.05, 0.01, 0.005, or
0.001.
[0075] A cell housing can comprise an electrically conductive
container and a conductor in electrical communication with a
current collector. The conductor protrudes through the container
through an aperture in the container and is electrically isolated
from the container. The ratio of the area of the aperture to the
area of the container may be less than about 0.3, 0.2, 0.15, 0.1,
0.05, 0.01, 0.005, or 0.001. The housing can be capable of
enclosing a cell that is capable of storing and/or taking in less
than 100 Wh of energy, about 100 Wh of energy, or more than 100 Wh
of energy. The cell can be capable of storing and/or taking in at
least about 1 Wh, 5 Wh, 25 Wh, 50 Wh, 100 Wh, 500 Wh, 1 kWh, 1.5
kWh, 2 kWh, 3 kWh, 5 kWh, 10 kWh, 15 kWh, 20 kWh, 30 kWh, 40 kWh,
or 50 kWh of energy.
[0076] FIG. 3 is a cross-sectional side view of an electrochemical
cell or battery 300 comprising a housing 301, an electrically
conductive feed-through (i.e., conductor, such as a conductor rod)
302 that passes through an aperture in the housing and is in
electrical communication with a liquid metal negative electrode
303, a liquid metal positive electrode 305, and a liquid salt
electrolyte 304 between the liquid metal electrodes 303, 305. The
cell or battery 300 can be configured for use with cell chemistries
operated under a low voltage mode ("Type 1 mode") or high voltage
mode ("Type 2 mode"), as disclosed elsewhere herein. The conductor
302 may be electrically isolated from the housing 301 (e.g., using
electrically insulating seals). The negative current collector 307
may comprise foam material that behaves like a sponge, and is
"soaked" in negative electrode liquid metal 303. The liquid metal
negative electrode 303 is in contact with the molten salt
electrolyte 304. The liquid salt electrolyte is also in contact
with the positive liquid metal electrode 305. The positive liquid
metal electrode 305 can be in electrical communication with the
housing 301 along the side walls and/or along the bottom end wall
of the housing.
[0077] The housing may include a container and a container lid
(e.g., cell cap). The container and container lid may be connected
mechanically. The negative current lead may be electrically
isolated from the container and/or container lid (e.g., cell cap),
via, for example, the use of an electrically insulating hermetic
seal. In some examples, an electrically insulating barrier (e.g.,
seal) may be provided between the negative current lead and the
container lid. As an alternative, the seal can be in the form of a
gasket, for example, and placed between the container lid, and the
container. In some examples, the electrochemical cell or battery
300 may comprise two or more conductors passing through one or more
apertures and in electrical communication with the liquid metal
negative electrode 303. In some instances, a separator structure
(not shown) may be arranged within the electrolyte 304 between the
liquid negative electrode 303 and the (liquid) positive electrode
305.
[0078] The housing 301 can be constructed from an electrically
conductive material such as, for example, steel, iron, stainless
steel, graphite, nickel, nickel based alloys, titanium, aluminum,
molybdenum, tungsten, or conductive compounds such as nitrides
(e.g., silicon carbide or titanium carbide), or a combination
thereof (e.g., alloy).
[0079] The housing 301 can comprise a housing interior 306. The
housing interior 306 may include, but is not limited to, a sheath
(e.g., a graphite sheath), a coating, a crucible (e.g., a graphite
crucible), a surface treatment, a lining, or any combination
thereof). In one example, the housing interior 306 is a sheath. In
another example, the housing interior 306 is a crucible. In yet
another example, examples, the housing interior 306 is a coating or
surface treatment. The housing interior 306 may be thermally
conductive, thermally insulating, electrically conductive,
electrically insulating, or any combination thereof. In some cases,
the housing interior 306 may be provided for protection of the
housing (e.g., for protecting the stainless steel material of the
housing from corrosion). In some cases, the housing interior can be
anti-wetting to the liquid metal positive electrode. In some cases,
the housing interior can be anti-wetting to the liquid
electrolyte.
[0080] The housing may comprise a thinner lining component of a
separate metal or compound, or a coating (e.g., an electrically
insulating coating), such as, for example, a steel housing with a
graphite lining, or a steel housing with a nitride coating or
lining (e.g., boron nitride, aluminum nitride), a titanium coating
or lining, or a carbide coating or lining (e.g., silicon carbide,
titanium carbide). The coating can exhibit favorable properties and
functions, including surfaces that are anti-wetting to the positive
electrode liquid metal. In some cases, the lining (e.g., graphite
lining) can be dried by heating above room temperature in air or
dried in a vacuum oven before or after being placed inside the cell
housing. Drying or heating the lining can remove moisture from the
lining prior to adding the electrolyte, positive electrode, or
negative electrode to the cell housing.
[0081] The housing 301 may include a thermally and/or electrically
insulating sheath or crucible 306. In this configuration, the
negative electrode 303 may extend laterally between the side walls
of the housing 301 defined by the sheath or crucible without being
electrically connected (i.e., shorted) to the positive electrode
305. Alternatively, the negative electrode 303 may extend laterally
between a first negative electrode end 303a and a second negative
electrode end 303b. When the sheath or crucible 306 is not
provided, the negative electrode 303 may have a diameter (or other
characteristic dimension, illustrated in FIG. 3 as the distance
from 303a to 303b) that is less than the diameter (or other
characteristic dimension such as width for a cuboid container,
illustrated in FIG. 3 as the distance D) of the cavity defined by
the housing 301.
[0082] The crucible can be made to be in electronic contact with
the cell housing by means of a thin layer of a conductive liquid
metal or semi-solid metal alloy located between the crucible and
the cell housing, such as the elements Pb, Sn, Sb, Bi, Ga, In, Te,
or a combination thereof.
[0083] The housing interior (e.g., sheath, crucible and/or coating)
306 can be constructed from a thermally insulating, thermally
conductive, and/or electrically insulating or electrically
conductive material such as, for example, graphite, carbide (e.g.,
SiC, TiC), nitride (e.g., BN), alumina, titania, silica, magnesia,
boron nitride, or a mixed oxide, such as, for example, calcium
oxide, aluminum oxide, silicon oxide, lithium oxide, magnesium
oxide, etc. For example, as shown in FIG. 3, the sheath (or other)
housing interior 306 has an annular cross-sectional geometry that
can extend laterally between a first sheath end 306a and a second
sheath end 306b. The sheath may be dimensioned (illustrated in FIG.
3 as the distance from 306a to 306b) such that the sheath is in
contact and pressed up against the side walls of the cavity defined
by the housing cavity 301. As an alternative, the housing interior
306 can be used to prevent corrosion of the container and/or
prevent wetting of the cathode material up the side wall, and may
be constructed out of an electronically conductive material, such
as steel, stainless steel, tungsten, molybdenum, nickel, nickel
based alloys, graphite, titanium, or titanium nitride. For example,
the sheath may be very thin and may be a coating. The coating can
cover just the inside of the walls, and/or, can also cover the
bottom of the inside of the container. In some cases, the sheath
(e.g., graphite sheath) may be dried by heating above room
temperature in air or dried in a vacuum oven before or after being
placed inside the cell housing. Drying or heating the lining may
remove moisture from the lining prior to adding the electrolyte,
positive electrode, or negative electrode to the cell housing.
[0084] Instead of a sheath, the cell may comprise an electrically
conductive crucible or coating that lines the side walls and bottom
inner surface of the cell housing, referred to as a cell housing
liner, preventing direct contact of the positive electrode with the
cell housing. The cell housing liner may prevent wetting of the
positive electrode between the cell housing and the cell housing
liner or sheath and may prevent direct contact of the positive
electrode on the bottom surface of the cell housing. The sheath may
be very thin and can be a coating. The coating can cover just the
inside of the walls, and/or, can also cover the bottom of the
inside of the container. The sheath may not fit perfectly with the
housing 301 which may hinder the flow of current between the cell
lining and the cell housing. To ensure adequate electronic
conduction between the cell housing and the cell lining, a liquid
of metal that has a low melting point (e.g., Pb, Sn, Bi), can be
used to provide a strong electrical connection between the
sheath/coating and the cell housing. This layer can allow for
easier fabrication and assembly of the cell.
[0085] The housing 301 can also include a first (e.g., negative)
current collector or lead 307 and a second (e.g., positive) current
collector 308. The negative current collector 307 may be
constructed from an electrically conductive material such as, for
example, nickel-iron (Ni--Fe) foam, perforated steel disk, sheets
of corrugated steel, sheets of expanded metal mesh, etc. The
negative current collector 307 may be configured as a plate or foam
that can extend laterally between a first collector end 307a and a
second collector end 307b. The negative current collector 307 may
have a collector diameter that is less than or similar to the
diameter of the cavity defined by the housing 301. In some cases,
the negative current collector 307 may have a collector diameter
(or other characteristic dimension, illustrated in FIG. 3 as the
distance from 307a to 307b) that is less than or similar to the
diameter (or other characteristic dimension, illustrated in FIG. 3
as the distance from 303a to 303b) of the negative electrode 303.
The positive current collector 308 may be configured as part of the
housing 301; for example, the bottom end wall of the housing may be
configured as the positive current collector 308, as illustrated in
FIG. 3. Alternatively, the current collector may be discrete from
the housing and may be electrically connected to the housing. In
some cases, the positive current collector may not be electrically
connected to the housing. The present disclosure is not limited to
any particular configurations of the negative and/or positive
current collector configurations.
[0086] The negative electrode 303 can be contained within the
negative current collector (e.g., foam) 307. In this configuration,
the electrolyte layer comes up in contact with the bottom, sides,
and/or the top of the foam 307. The metal contained in the foam
(i.e., the negative electrode material) can be held away from the
sidewalls of the housing 301, such as, for example, by the
absorption and retention of the liquid metal negative electrode
into the foam, thus allowing the cell to run without the insulating
sheath 306. In some cases, a graphite sheath or graphite cell
housing liner (e.g., graphite crucible) may be used to prevent the
positive electrode from wetting up along the side walls, which can
prevent shorting of the cell.
[0087] Current may be distributed substantially evenly across a
positive and/or negative liquid metal electrode in contact with an
electrolyte along a surface (i.e., the current flowing across the
surface may be uniform such that the current flowing through any
portion of the surface does not substantially deviate from an
average current density). In some examples, the maximum density of
current flowing across an area of the surface is less than about
105%, or less than or equal to about 115%, less than or equal to
about 125%, less than or equal to about 150%, less than or equal to
about 175%, less than or equal to about 200%, less than or equal to
about 250%, or less than or equal to about 300% of the average
density of current flowing across the surface. In some examples,
the minimum density of current flowing across an area of the
surface is greater than or equal to about 50%, greater than or
equal to about 60%, greater than or equal to about 70%, greater
than or equal to about 80%, greater than or equal to about 90%, or
greater than or equal to about 95% of the average density of
current flowing across the surface.
[0088] Viewed from a top or bottom direction, as indicated
respectively by "TOP VIEW" and "BOTTOM VIEW" in FIG. 3, the
cross-sectional geometry of the cell or battery 300 can be
circular, elliptical, square, rectangular, polygonal, curved,
symmetric, asymmetric or any other compound shape based on design
requirements for the battery. In an example, the cell or battery
300 is axially symmetric with a circular or square cross-section.
Components of cell or battery 300 (e.g., component in FIG. 3) may
be arranged within the cell or battery in an axially symmetric
fashion. In some cases, one or more components may be arranged
asymmetrically, such as, for example, off the center of the axis
309.
[0089] The combined volume of positive and negative electrode
material may be at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%,
70%, 80%, 90%, or 95% of the volume of the battery (e.g., as
defined by the outer-most housing of the battery, such as a
shipping container). In some cases, the combined volume of anode
and cathode material is at least about 5%, at least about 10%, at
least about 20%, at least about 30%, at least about 40%, at least
about 60%, at least about 75%, of the volume of the cell. The
combined volume of the positive and negative electrodes material
may increase or decrease (e.g., in height) during operation due to
growth or expansion, or shrinkage or contraction, respectively, of
the positive or negative electrode. In an example, during
discharge, the volume of the negative electrode (anode during
discharge) may be reduced due to transfer of the negative electrode
material to the positive electrode (cathode during discharge),
wherein the volume of the positive electrode is increased (e.g., as
a result of an alloying reaction). The volume reduction of the
negative electrode may or may not equal the volume increase of the
positive electrode. The positive and negative electrode materials
may react with each other to form a solid or semi-solid mutual
reaction compound (also "mutual reaction product" herein), which
may have a density that is the same, lower, or higher than the
densities of the positive and/or negative electrode materials.
Although the mass of material in the electrochemical cell or
battery 300 may be constant, one, two or more phases (e.g., liquid
or solid) may be present, and each such phase may comprise a
certain material composition (e.g., an alkali metal may be present
in the materials and phases of the cell at varying concentrations:
a liquid metal negative electrode may contain a high concentration
of an alkali metal, a liquid metal positive electrode may contain
an alloy of the alkali metal and the concentration of the alkali
metal may vary during operation, and a mutual reaction product of
the positive and negative liquid metal electrodes may contain the
alkali metal at a fixed or variable stoichiometry). The phases
and/or materials may have different densities. As material is
transferred between the phases and/or materials of the electrodes,
a change in combined electrode volume may result.
[0090] In some cases, a cell can include one or more alloyed
products that are liquid, semi-liquid (or semi-solid), or solid.
The alloyed products can be immiscible with the negative electrode,
positive electrode and/or electrolyte. The alloyed products can
form from electrochemical processes during charging or discharging
of a cell.
[0091] An alloyed product can include an element constituent of a
negative electrode, positive electrode and/or electrolyte. An
alloyed product can have a different density than the negative
electrode, positive electrode or electrolyte, or a density that is
similar or substantially the same. The location of the alloyed
product can be a function of the density of the alloyed product
compared to the densities of the negative electrode, electrolyte
and positive electrode. The alloyed product can be situated in the
negative electrode, positive electrode or electrolyte, or at a
location (e.g., interface) between the negative electrode and the
electrolyte or between the positive electrode and the electrolyte,
or any combination thereof. In an example, an alloyed product is an
intermetallic between the positive electrode and the electrolyte
(see, for example, FIG. 4). In some cases, some electrolyte can
seep in between the intermetallic and the positive electrode. In
other examples, the alloyed product can be at other locations
within the cell and be formed of a material of different
stoichiometries/compositions, depending on the chemistry,
temperature, and/or charge state of the cell.
[0092] FIG. 4 is a cross-sectional side view of an electrochemical
cell or battery 400 with an intermetallic layer 410. The
intermetallic layer 410 can include a mutual reaction compound of a
material originating from the negative electrode 403 and positive
electrode material 405. For example, a negative liquid metal
electrode 403 can comprise an alkali or alkaline earth metal (e.g.,
Na, Li, K, Mg, or Ca), the positive liquid metal electrode 405 can
comprise one or more of transition metal, d-block (e.g., Group 12),
Group IIIA, IVA, VA or VIA elements (e.g., lead and/or antimony),
and the intermetallic layer 410 can comprise a mutual reaction
compound or product thereof (e.g., alkali plumbide or antimonide,
e.g., Na.sub.3Pb, Li.sub.3Sb, K.sub.3Sb, Mg.sub.3Sb.sub.2, or
Ca.sub.3Sb.sub.2). An upper interface 410a of the intermetallic
layer 410 is in contact with the electrolyte 404, and a lower
interface 410b of the intermetallic layer 410 is in contact with
the positive electrode 405. The mutual reaction compound may be
formed during discharging at an interface between a positive liquid
metal electrode (liquid metal cathode in this configuration) 405
and a liquid salt electrolyte 404. The mutual reaction compound (or
product) can be solid or semi-solid. In an example, the
intermetallic layer 410 can form at the interface between the
liquid metal cathode 405 and the liquid salt electrolyte 404. In
some cases, the intermetallic layer 410 may exhibit liquid
properties (e.g., the intermetallic may be semi-solid, or it may be
of a higher viscosity or density than one or more adjacent
phases/materials).
[0093] The cell 400 comprises a first current collector 407 and a
second current collector 408. The first current collector 407 is in
contact with the negative electrode 403, and the second current
collector 408 is in contact with the positive electrode 405. The
first current collector 407 is in contact with an electrically
conductive feed-through 402. A housing 401 of the cell 400 can
include a thermally and/or electrically insulating sheath 406. In
an example, the negative liquid metal electrode 403 includes
magnesium (Mg), the positive liquid metal electrode 405 includes
antimony (Sb), and the intermetallic layer 410 includes Mg and Sb
(Mg.sub.xSb, where `x` is a number greater than zero), such as, for
example, magnesium antimonide (Mg.sub.3Sb.sub.2). Cells with a
Mg.parallel.Sb chemistry may contain magnesium ions within the
electrolyte as well as other salts (e.g., MgCl.sub.2, NaCl, KCl, or
a combination thereof). In some cases, in a discharged state, the
cell is deficient in Mg in the negative electrode and the positive
electrode comprises and alloy of Mg--Sb. In such cases, during
charging, Mg is supplied from the positive electrode, passes
through the electrolyte as a positive ion, and deposits onto the
negative current collector as Mg. In some examples, the cell has an
operating temperature of at least about 550.degree. C., 600.degree.
C., 650.degree. C., 700.degree. C., or 750.degree. C., and in some
cases between about 650.degree. C. and about 750.degree. C. In a
charged state, all or substantially all the components of the cell
can be in a liquid state. Alternative chemistries exist, including
Ca--Mg.parallel.Bi comprising a calcium halide constituent in the
electrolyte (e.g., CaF.sub.2, KF, LiF, CaCl.sub.2, KCl, LiCl,
CaBr.sub.2, KBr, LiBr, or combinations thereof) and operating above
about 500.degree. C., Ca--Mg.parallel.Sb--Pb comprising a calcium
halide constituent in the electrolyte (e.g., CaF.sub.2, KF, LiF,
CaCl.sub.2, KCl, LiCl, CaBr.sub.2, KBr, LiBr, or combinations
thereof) and operating above about 500.degree. C.,
Li.parallel.Pb--Sb cells comprising a lithium-ion containing halide
electrolyte (e.g., LiF, LiCl, LiBr, or combinations thereof) and
operating between about 350.degree. C. and about 550.degree. C.,
and Na.parallel.Pb cells comprising a sodium halide as part of the
electrolyte (e.g., NaCl, NaBr, NaI, NaF, LiCl, LiF, LiBr, LiI, KCl,
KBr, KF, KI, CaCl.sub.2, CaF.sub.2, CaBr.sub.2, CaI.sub.2, or
combinations thereof) and operating above about 300.degree. C. In
some cases, the product of the discharge reaction may be an
intermetallic compound (e.g., Mg.sub.3Sb.sub.2 for the
Mg.parallel.Sb cell chemistry, Li.sub.3Sb for the
Li.parallel.Pb--Sb chemistry, Ca.sub.3Bi.sub.2 for the
Ca-Mg.parallel.Bi chemistry, or Ca.sub.3Sb.sub.2 for the
Ca-Mg.parallel.Pb-Sb chemistry), where the intermetallic layer may
develop as a distinct solid phase by, for example, growing and
expanding horizontally along a direction x and/or growing or
expanding vertically along a direction y at the interface between
the positive electrode and the electrolyte. The growth may be
axially symmetrical or asymmetrical with respect to an axis of
symmetry 409 located at the center of the cell or battery 400.
[0094] Type 1 and Type 2 Modes of Operation
[0095] Liquid metal batteries can provide a distinguished
opportunity to achieve a long lifespan system that is relatively
simple to assemble. A cell of a liquid metal battery of the present
disclosure may be operated in a manner that utilizes symmetric or
substantially symmetric electrode reactions in the form of an
alloying/de-alloying electrochemical reaction (referred to herein
as "low voltage operation" mode, or "Type 1" mode). In some cases,
in Type 1 mode, a cell is operated at a voltage from about 0.4 Volt
(V) to about 1.5 V. Here, one active metal species may be present
in the negative electrode and as an alloyed species in the positive
electrode, and may be the only metal species that dissolves in or
is extracted from the electrolyte during cell discharging and
charging, respectively. The composition of the electrolyte
therefore may not substantially change during the low voltage
operation mode. Such mode of operation may provide a relatively low
cell voltage, resulting in a relatively low energy density.
[0096] In an example Type 1 cell, upon discharging, cations formed
at the negative electrode can migrate into the electrolyte.
Concurrently, the electrolyte can provide a cation of the same
species (e.g., the cation of the negative electrode material) to
the positive electrode, which can reduce from a cation to a
neutrally charged metallic species, and alloy with the positive
electrode. In a discharged state, the negative electrode can be
depleted (e.g., partially or fully) of the negative electrode
material (e.g., Li, Na, K, Mg, Ca). During charging, the alloy at
the positive electrode can disassociate to yield cations of the
negative electrode material (e.g., Li.sup.+, Na.sup.+, K.sup.+,
Mg.sup.2+, Ca.sup.2+), which migrates into the electrolyte. The
electrolyte can then provide cations (e.g., the cation of the
negative electrode material) to the negative electrode, where the
cations accept one or more electrons from an external circuit and
are converted back to a neutral metal species, which replenishes
the negative electrode to provide a cell in a charged state. A Type
1 cell can operate in a push-pop fashion, in which the entry of a
cation into the electrolyte results in the discharge of the same
cation from the electrolyte.
[0097] A second mode in which liquid metal battery cells of the
present disclosure can operate involves a non-symmetric or
substantially non-symmetric reaction where one metal species is
electrochemically active at one electrode and a second metal
species is electrochemically active at the other electrode,
resulting in a net change in the composition of the electrolyte at
different states of charge. This mode of operation (referred to
herein as "high voltage operation" mode, "Type 2" mode, or cells
using "displacement salt electrode" operation or mechanism) can
initiate new chemical reactions compared to the Type 1 mode of
operation (e.g., in addition to or instead of alloying reaction at
the positive electrode), in some cases resulting in, or otherwise
utilizing, a relatively higher cell voltage (e.g., 1.5 V to 2.5 V,
1 V to 3 V, or 1 V to 4 V). Type 2 mode of operation can offer the
possibility of using a wider variety of active materials, and
combinations of such materials, as the electrochemistry of the
cell.
[0098] In an example Type 2 cell, in a discharged state the
electrolyte comprises cations of the negative electrode material
(e.g., Li.sup.+, Na.sup.+, K.sup.+, Mg.sup.2+, Ca.sup.2+), and the
positive electrode comprises positive electrode material (e.g., Sb,
Pb, Sn, Zn, Hg). During charging, a cation of the negative
electrode material from the electrolyte accepts one or more
electrons (e.g., from a negative current collector) to form the
negative electrode comprising the negative electrode material. In
some examples, the negative electrode material is liquid and wets
into a foam (or porous) structure of the negative current
collector. In some examples, negative current collector may not
comprise foam (or porous) structure. In some examples, the negative
current collector may comprise a metal, such as, for example,
tungsten (e.g., to avoid corrosion from Zn), tungsten carbide or
molybdenum negative collector not comprising Fe--Ni foam.
Concurrently, positive electrode material from the positive
electrode sheds electrons (e.g., to a positive current collector)
and dissolves into the electrolyte as cations of the positive
electrode material (e.g., Sb.sup.3+, Pb.sup.2+, Sn.sup.2+,
Zn.sup.2+, Hg.sup.2+). The concentration of the cations of the
positive electrode material can vary in vertical proximity within
the electrolyte (e.g., as a function of distance above the positive
electrode material) based on the atomic weight and diffusion
dynamics of the cation material in the electrolyte. In some
examples, the cations of the positive electrode material are
concentrated in the electrolyte near the positive electrode.
[0099] In some examples, a Type 1 cell includes a negative
electrode comprising an alkali or alkaline earth metal (e.g.,
lithium, sodium, potassium, magnesium, calcium), and a positive
electrode comprising a poor metal, or alloys of such metals (e.g.,
one or more of tin, lead, bismuth, antimony, tellurium and
selenium). The negative electrode and positive electrode can be in
a liquid (or molten) state at an operating temperature of the cell.
The negative and positive electrodes can be separated by a salt
electrolyte (e.g., alkali or alkaline earth metal halide
salts).
[0100] In a charged state, a Type 1 cell, when operated under Type
2 mode, can have a voltage of at least about 0.5 V, 1 V, 1.5 V, 2
V, 2.5 V, or 3 V in a charged state. In some cases, a Type 1 cell,
when operated under Type 2 mode, can have an open circuit voltage
(OCV) of at least about 0.5 V, 1 V, 1.5 V, 2 V, 2.5 V, or 3 V. In
an example, a Type 1 cell, when operated under Type 2 mode, has an
open circuit voltage greater than about 1 V, greater than about 2
V, or greater than about 3 V. In some cases, a charge cutoff
voltage (CCV) of a Type 1 cell, when operated in Type 2 mode, is
from about 1 V to 3 V, 1.5 V to 2.5 V, 1.5 V to 3 V, or 2 V to 3 V
in a charged state. In some cases, a charge cutoff voltage (CCV) of
a Type 1 cell, when operated in Type 2 mode, is at least about 1.0
V, 1.1 V, 1.2 V, 1.3 V, 1.4 V, 1.5 V, 1.6 V, 1.7 V, 1.8 V, 1.9 V,
2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, 2.6 V, 2.7 V, 2.8 V, 2.9
V or 3.0 V. In an example, a Type 1 cell, when operated under Type
2 mode, has a charge cutoff voltage of at least about 1.7 V after
at least about 100 charge/discharge cycles. In some cases, a
voltage of a Type 1 cell, when operated in Type 2 mode, is from
about 1 V to 3 V, 1.5 V to 2.5 V, 1.5 V to 3 V, or 2 V to 3 V in a
charged state. A Type 1 cell can provide such voltage(s) (e.g.,
voltage, OCV and/or CCV) upon operating at up to and exceeding
about 10 cycles, 20 cycles, 30 cycles, 40 cycles, 50 cycles, 100
cycles, 200 cycles, 300 cycles, 400 cycles, 500 cycles, 600 cycles,
700 cycles, 800 cycles, 900 cycles, 1000 cycles, 2000 cycles, 3000
cycles, 4000 cycles, 5000 cycles, 10,000 cycles, or 20,000 cycles
(also "charge/discharge cycles" herein). In some cases, the
limiting factor on the number of cycles may be dependent on, for
example, the housing and/or the seal as opposed to the chemistry of
the negative electrode, electrolyte and/or the positive electrode.
The limit in cycles may be dictated not by the electrochemistry,
but by the degradation of non-active components of the cell, such
as the container. During operation at an operating temperature of
the Type 1 cell, the Type 1 cell can have a negative electrode,
electrolyte and positive electrode in a liquid (or molten)
state.
[0101] A Type 1 cell of the present disclosure, when operated in
Type 2 mode, can have an energy storage capacity of at least about
1 Wh, 5 Wh, 25 Wh, 50 Wh, 100 Wh, 500 Wh, 1 kWh, 1.5 kWh, 2 kWh, 3
kWh, 5 kWh, 10 kWh, 15 kWh, 20 kWh, 30 kWh, 40 kWh, or 50 kWh, and
a current density of at least about 10 mA/cm.sup.2, 20 mA/cm.sup.2,
30 mA/cm.sup.2, 40 mA/cm.sup.2, 50 mA/cm.sup.2, 60 mA/cm.sup.2, 70
mA/cm.sup.2, 80 mA/cm.sup.2, 90 mA/cm.sup.2, 100 mA/cm.sup.2, 200
mA/cm.sup.2, 300 mA/cm.sup.2, 400 mA/cm.sup.2, 500 mA/cm.sup.2, 600
mA/cm.sup.2, 700 mA/cm.sup.2, 800 mA/cm.sup.2, 900 mA/cm.sup.2, 1
A/cm.sup.2, 2 A/cm.sup.2, 3 A/cm.sup.2, 4 A/cm.sup.2, 5 A/cm.sup.2,
or 10 A/cm.sup.2.
[0102] In a charged state, a Type 1 cell, when operated under Type
1 mode, can have a voltage of at least about 0.5 V, 0.6 V, 0.7 V,
0.8 V, 0.9 V, 1 V, 1.2 V, or 1.5 V in a charged state. In some
cases, a Type 1 cell, when operated under Type 1 mode, can have an
open circuit voltage (OCV) of at least about 0.5 V, 0.6 V, 0.7 V,
0.8 V, 0.9 V, 1 V, 1.2 V, or 1.5 V. In an example, a Type 1 cell,
when operated under Type 1 mode, has an open circuit voltage
greater than about 0.5 V. In some cases, a charge cutoff voltage
(CCV) of a Type 1 cell, when operated in Type 1 mode, is from about
0.5 V to 1.5 V in a charged state. In some cases, a charge cutoff
voltage (CCV) of a Type 1 cell, when operated in Type 1 mode, is at
least about 0.5 V, 0.6 V, 0.7 V, 0.8 V, 0.9 V, 1.0 V, 1.1 V, 1.2 V,
1.3 V, 1.4 V, or 1.5 V. In an example, a Type 1 cell, when operated
under Type 1 mode, has a charge cutoff voltage of at least about
1.0 V after at least about 300 charge/discharge cycles. In some
cases, a voltage of a Type 1 cell, when operated in Type 1 mode, is
from about 0.5 V to 1.5 V in a charged state. A Type 1 cell can
provide such voltage(s) (e.g., voltage, OCV and/or CCV) upon
operating at up to and exceeding about 10 cycles, 20 cycles, 30
cycles, 40 cycles, 50 cycles, 100 cycles, 200 cycles, 300 cycles,
400 cycles, 500 cycles, 600 cycles, 700 cycles, 800 cycles, 900
cycles, 1000 cycles, 2000 cycles, 3000 cycles, 4000 cycles, 5000
cycles, 10,000 cycles, or 20,000 cycles. In some cases, the
limiting factor on the number of cycles may be dependent on, for
example, the housing and/or the seal as opposed to the chemistry of
the negative electrode, electrolyte and/or the positive electrode.
The limit in cycles may be dictated not by the electrochemistry,
but by the degradation of non-active components of the cell, such
as the container. During operation at an operating temperature of
the Type 1 cell, the Type 1 cell can have a negative electrode,
electrolyte and positive electrode in a liquid (or molten)
state.
[0103] A Type 1 cell of the present disclosure, when operated in
Type 1 mode, can have an energy storage capacity of at least about
1 Wh, 5 Wh, 25 Wh, 50 Wh, 100 Wh, 500 Wh, 1 kWh, 1.5 kWh, 2 kWh, 3
kWh, 5 kWh, 10 kWh, 15 kWh, 20 kWh, 30 kWh, 40 kWh, or 50 kWh, and
a current density of at least about 10 mA/cm.sup.2, 20 mA/cm.sup.2,
30 mA/cm.sup.2, 40 mA/cm.sup.2, 50 mA/cm.sup.2, 60 mA/cm.sup.2, 70
mA/cm.sup.2, 80 mA/cm.sup.2, 90 mA/cm.sup.2, 100 mA/cm.sup.2, 200
mA/cm.sup.2, 300 mA/cm.sup.2, 400 mA/cm.sup.2, 500 mA/cm.sup.2, 600
mA/cm.sup.2, 700 mA/cm.sup.2, 800 mA/cm.sup.2, 900 mA/cm.sup.2, 1
A/cm.sup.2, 2 A/cm.sup.2, 3 A/cm.sup.2, 4 A/cm.sup.2, 5 A/cm.sup.2,
or 10 A/cm.sup.2.
[0104] The present disclosure provides cell design criteria that
may address failure mechanisms, enabling the cells to achieve a
long lifespan and optimum performance. Type 2 cell operation can
advantageously provide opportunities for new cell chemistries that
are lower cost, less hazardous and/or nontoxic, and that use more
earth abundant materials.
[0105] The present disclosure provides various non-limiting
approaches for operating cells under the Type 2 mode. In a first
approach, a cell with positive and negative electrode materials
that are ordinarily configured for use in a Type 1 mode is operated
in a Type 2 mode of operation. In a second approach, a cell
comprises materials that are configured for use in Type 2 mode of
operation.
[0106] Under the first approach, a cell configured for use in a
Type 1 mode is operated in Type 2 mode (e.g., voltage from 1.5 V to
2.5 V or higher), for example by charging the cell to a higher
voltage and/or having less negative electrode material in the cell.
Any operationally requisite negative electrode material can be
supplied by the electrolyte during cell charging. In an example,
the Type 1 cell may be Li.parallel.Pb or Li.parallel.Sb-Pb or
Li.parallel.Zn-Sn or Li.parallel.Bi with a lithium-ion containing
electrolyte (e.g., LiF, LiCl, LiBr or a combination thereof). The
cell is deficient in Li in the negative electrode, but during cell
charging Li is supplied from the electrolyte to the negative
electrode. In some examples, the Type 1 cell has an operating
temperature of at least about 200.degree. C., at least about
250.degree. C., at least about 300.degree. C., at least about
400.degree. C., at least about 450.degree. C., at least about
500.degree. C., or at least about 550.degree. C., in some cases
between about 500.degree. C. and 550.degree. C. In a charged state,
all or substantially all of the components of the Type 1 cell are
in a liquid state.
[0107] Under Type 1 mode, the Type 1 cell can be charged to a
voltage from about 0.5 V to 1.5 V to attain a charged or
substantially charged state, and subsequently discharged to attain
a discharged or substantially discharged state. However, under Type
2 mode, the Type 1 cell can be charged to a voltage from about 1.5
V to 2 V or higher (e.g., 1.5 V to 4 V). The quantity of lithium in
the negative electrode in such a case can be in stoichiometric
balance with the quantity of Sb and/or Pb in the positive
electrode. As an alternative, the Type 1 cell can have a negative
electrode with a stoichiometric deficiency of a negative electrode
material (e.g., Li). Under Type 2 mode (e.g., at a CCV from about
1.5 V to 2.5 V or higher), during charging, one or more components
of the positive electrode (e.g., Pb or Sb) can be removed from the
positive electrode and dissolved into the electrolyte as a cation
(e.g., Pb.sup.+2 or Sb.sup.3+). Concurrently, one or more
components of the negative electrode (e.g., Li) can be removed from
the electrolyte, in its ionic form (e.g., Li.sup.+), and deposited
into the negative electrode in metallic form. A cell thus formed
can have a higher chemical potential relative to a cell operating
under the Type 1 mode.
[0108] A Type 1 cell can have any cell and seal configuration
disclosed herein. For instance, the active cell materials can be
held within a sealed steel/stainless steel container with a high
temperature seal on the cell lid. A negative current lead can pass
through the cell lid (and be sealed to the cell lid by the
dielectric high temperature seal), and connect with a porous
negative current collector (e.g., metal foam) suspended in an
electrolyte. In some cases, the cell can use a graphite sheath,
coating, crucible, surface treatment or lining (or any combination
thereof) on the inner wall of the cell crucible. In other cases,
the cell may not use a graphite sheath, coating, crucible, surface
treatment or lining on an inner wall of the cell crucible.
[0109] In an example, a Li.parallel.Pb cell with a lithium halide
(e.g., LiF, LiCl, LiBr or a combination thereof) electrolyte that
is configured for use as a Type 1 cell can operate in Type 2 mode
through the following example reactions: during charging, Li.sup.+
ions from the electrolyte accept an electron from the top/negative
current collector (e.g., foam current collector) and deposit as
liquid Li metal, wetting into the foam/porous structure.
Concurrently, Pb atoms shed electrons and subsequently dissolve
into the electrolyte as Pb.sup.2+. The Pb.sup.2+ ions and
respective halide salt (e.g., PbC1.sub.2) can be more dense than
the remainder of the lithium halide electrolyte. Hence, Pb.sup.2+
ion species may be driven by gravitation to remain concentrated
towards the positive electrode. The Pb.sup.2+ ions may be
concentrated at the bottom of the electrolyte layer. Since Li metal
is deposited onto the foam from the electrolyte, the system may not
require any Li metal during the time of assembly, but rather, can
be assembled in a discharged state having only a Li salt
electrolyte and a Pb or Pb alloy (e.g., Pb--Sb) positive electrode.
In some examples, upon charge, the Li.parallel.Pb is charged until
a voltage of at least about 1.5 V, 2 V, 2.5 V, or 3 V or higher is
obtained. The voltage in some cases can be from about 1 V to 2 V, 1
V to 2.5 V, 1 V to 3 V, 1.5 V to 2.5 V, 1.5 V to 3 V, 2 V to 3 V,
1.5 V to 2.0 V, or 1.5 V to 2.5 V in a charged state.
[0110] During operation of a cell under Type 1 mode or Type 2 mode,
material of the positive electrode may dissolve in the electrolyte
and in some cases migrate to the negative electrode, where it may
deposit into the negative electrode or alloy with the material of
the negative electrode. In some situations, this may degrade the
operation of the cell through, for example, decreasing the
operating voltage of the cell. In addition to, or as an
alternative, a material of the negative electrode (e.g., Li) may
react with a material of the positive electrode (e.g., Pb) in the
electrolyte, which may form a particle cloud that may decrease cell
performance and in some cases cause a shorting path between the
negative and positive electrodes. The present disclosure provides
various approaches for minimizing the possibility of (i) material
of the positive electrode from depositing into the negative
electrode or alloying with the material of the negative electrode,
and (ii) material of the negative electrode from reacting with the
material of the positive electrode in the electrolyte. These
include, without limitation, selecting positive electrode
components to have requisite free energies of formation
(.DELTA.G.sub.f) with a halide salt, selecting a thickness of the
electrolyte as a function of relative density (compared to the
electrolyte density) and diffusion kinetics of dissolved positive
electrode species in the electrolyte, limiting a size or volume of
the negative electrode, allowing the cell to periodically rest in a
discharged state while held at a voltage below the Type 2 mode open
circuit voltage (OCV), operating a cell at lower charge capacity,
and operating the cell in both Type 1 and Type 2 modes of
operation. Some or all of these approaches may aid in improving
cell performance and minimizing the occurrence of cell failure of
Type 1 cells during Type 2 mode of operation, or Type 2 cells
during Type 2 mode of operation.
[0111] In some situations, the positive electrode can include a
plurality of components or materials (e.g., Pb and Sb). One of the
components (or materials) can have a less negative .DELTA.G.sub.f
with halide salts in the electrolyte than the other component(s).
For example, if the positive electrode comprises Pb and Sb, Sb has
a more negative .DELTA.G.sub.f with halide salts in the electrolyte
than Pb. The presence of an alloying metal can lower the activity
of Pb in the positive electrode. In such circumstances, during
charging, any droplets comprising a material of the positive
electrode (e.g., Pb) that form in the electrolyte may have a higher
activity than the material in the positive electrode, which, in
some cases, may provide a driving force that, over time, dissolves
the droplets in the electrolyte and deposits the droplets in the
positive electrode. Such configuration may be practical for both
Type 2 cells and Type 1 cells operated in Type 2 mode. Thus,
alloying a positive electrode material (e.g., Sb) with a less
electronegative positive electrode material (e.g., metal or
metalloid such as Pb) can be used to decrease or prevent build-up
of small particles of either positive electrode material (e.g., Sb
or Pb) from accumulating in the electrolyte. Such accumulation of
particles or phases may in some cases lead to electronic shorting
between the electrodes through the electrolyte.
[0112] The thickness of the electrolyte may be selected to improve
cell performance and operating lifetime. In some cases, the
thickness of the electrolyte layer can be selected to minimize, if
not substantially prevent, material of the positive electrode from
diffusing into the negative electrode during cell operation, such
as cell charging. The thickness of the electrolyte may be selected
to decrease the rate at which material of the positive electrode
diffuses into the negative electrode during cell operation, such as
cell charging and/or discharging, and can be a function of
diffusion kinetics and relative density of the positive electrode
ion species dissolved into the electrolyte.
[0113] In some examples, the electrolyte can have a thickness
(measured as the distance between negative electrode/electrolyte
and positive electrode/electrolyte interfaces) of at least about
0.01 cm, 0.05 cm, 0.1 cm, 0.5 cm, 0.8 cm, 1.0 cm, 1.3 cm, 1.5 cm, 2
cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm for a cell
having a thickness of at least about 1 cm, 2 cm, 3 cm, 4 cm, 5 cm,
6 cm, 7 cm, 8 cm, 9 cm, 10 cm or more. In some examples, a cell has
a thickness of at most about 3 cm or 4 cm, and an electrolyte with
a thickness of at most about 1 cm or 2 cm.
[0114] As an alternative, or in addition to, the size (e.g.,
volume) of the negative electrode can be selected such that, upon
cell charging, the negative current collector (e.g., metallic foam,
or a tungsten current collector or lead) becomes nearly,
substantially, or completely full of the negative electrode
material (e.g., Li or Na) such that if there is any additional
material from the electrolyte or positive electrode (e.g., Zn), it
may overflow and not react with, or deposit into, the negative
electrode. In an example, a cell comprises a negative electrode
comprising Li or Na and a positive electrode comprising Zn. Since
Zn is heavier (or more dense) than Li or Na, a Zn--Na or Zn--Li
alloy may drip or flow off the bottom of the negative electrode
(i.e., along the direction of the gravitational acceleration
vector) and recombine with the positive electrode. This can aid in
naturally cleansing the negative electrode of any Zn, such as, for
example, in cases in which the Zn alloy is relatively
anti-wetting/immiscible with the negative electrode material.
[0115] In an example, in a Type 2 cell chemistry, the negative
electrode and the positive electrode materials may form an
immiscible mixture (e.g., of Na-rich and Zn-rich composition). The
immiscible mixture may promote the positive electrode material rich
mixture to drip off the negative electrode and rejoin the positive
electrode, thereby recovering cross-contaminated cathode
material.
[0116] In some cases, a cell can be periodically permitted to rest
in a discharged state under voltage that is below the open circuit
voltage (OCV) in Type 2 mode. This approach can provide an
opportunity for any droplets, comprising positive electrode
material, that may have formed in the electrolyte or negative
current collector to settle down to the positive electrode and
recombine with the positive electrode material. In an example, a
cell comprises a negative electrode comprising Li or Na and a
positive electrode comprising Pb. During charging under Type 2
mode, Pb droplets form in the electrolyte. Subsequent to
discharging, the cell is permitted to rest for a given time period
at an applied voltage. In such a case, Pb droplets that have formed
in the electrolyte settle down (i.e., along the gravitational
acceleration vector) to the positive electrode, where they can
recombine with the positive electrode.
[0117] In some cases, a cell can be operated at a lower charge
capacity with respect to a maximum charge capacity of the cell,
which can limit the quantity of positive electrode material that
may dissolve in the electrolyte. In some examples, a cell can be
operated at a charge capacity that is about 95%, 90%, 80%, 70%,
60%, 50%, 40%, 30%, 10%, 5% of the maximum charge capacity
[0118] In some cases, a cell can be operated in both a high voltage
(Type 2) operating mode and the low voltage (Type 1) operating
mode. This may provide a driving force for the material of the
positive electrode (e.g., Pb.sup.2+) to redeposit onto the positive
electrode during the Type 1 mode, which can help minimize, if not
prevent, the material of the positive electrode form depositing in
the electrolyte or the negative electrode.
[0119] A cell can be cycled between Type 1 and Type 2 modes of
operation. A cell can be initially charged (or discharged) under
Type 1 mode to a given voltage (e.g., 0.5 V to 1 V), and
subsequently charged (then discharged) under Type 2 mode to a
higher voltage (e.g., 1.5 V to 2.5 V, or 1.5 V to 3 V).
[0120] During cell operation, material (e.g., Fe) from a wall of
the cell can react under the higher voltage potential (e.g., Type 2
mode), and ionize as a soluble species in the electrolyte. Hence,
the wall material can dissolve into the electrolyte and
subsequently interfere with the cell's electrochemistry. For
example, the dissolved material can deposit on the negative
electrode, which, in some cases, can grow as dendrites and stretch
across the electrolyte to one or more walls of the cell, or toward
the positive electrode, which can result in a short failure. The
present disclosure provides various approaches for suppressing or
otherwise helping minimize the dissolution of solid (passive) cell
material such as Fe and its potentially negative effects on cell
performance by, for example, formation of dendrites and cell
shorting. In some cases, a cell can be designed such that increased
spacing between the negative electrode and a wall of the cell
suppresses or otherwise helps minimize the ability of dendrites
from forming and shorting the wall to the inner wall. A cell can
include an electrically insulating, and chemically stable sheath or
coating between one or more walls of the cell and the negative
electrode, electrolyte and/or positive electrode to minimize or
prevent shorting to the one or more walls of the cell. In some
cases, the cell can be formed of a non-ferrous container or
container lining, such as a carbon-containing material (e.g.,
graphite), or a carbide (e.g., SiC, TiC), or a nitride (e.g., TiN,
BN), or a chemically stable metal (e.g., Ti, Ni, B). The container
or container lining material may be electrically conductive. Such
non-limiting approaches can be used separately or in combination,
for suppressing or otherwise helping minimize chemical interactions
with Fe or other cell wall materials, and any subsequent negative
effects on cell performance.
[0121] Although electrochemical cells of the present disclosure
have been described, in some examples, as operating in a Type 1
mode or Type 2 mode, other modes of operation are possible. Type 1
mode and Type 2 mode are provided as examples and are not intended
to limit the various modes of operation of electrochemical cells
disclosed herein.
[0122] Type 2 Chemistries
[0123] Another aspect of the present disclosure provides Type 2
cell chemistries. In some cases, cells operated under Type 2 mode
can operate at a voltage between electrodes that can exceed those
of cells operated under Type 1 mode. In some cases, Type 2 cell
chemistries can operate at a voltage between electrodes that can
exceed those of Type 1 cell chemistries operated under Type 1 mode.
Type 2 cells can be operated in Type 2 mode. During operation at an
operating temperature of the Type 2 cell, the Type 2 cell can have
a negative electrode, electrolyte and positive electrode in a
liquid (or molten) state. A cell can include components that are
solid or semi-solid, such as a solid intermetallic layer between
the electrolyte and the positive electrode. Products of the
electrochemical cycle may include the formation of alloyed species
that may be liquid, semi-liquid, or solid, and may be soluble
and/or immiscible with the electrode materials and/or the
electrolyte salt. In some cases, the intermetallic layer is
observed under Type 1 mode of operation but not Type 2 mode of
operation. For example, the intermetallic layer (e.g., the
intermetallic layer in FIG. 4) may not form during operation of a
Type 2 cell.
[0124] A Type 2 cell operating in Type 2 mode can have components
(e.g., negative electrode, electrolyte, positive electrode) that
are fully liquid. A Type 2 cell operating in Type 2 mode can have
solid or semi-solid components, such as an intermetallic.
[0125] A cell with a Type 2 chemistry can include a molten alkali
or alkaline earth metal (e.g., lithium, magnesium, sodium) negative
electrode and an electrolyte adjacent to the negative electrode.
The electrolyte can include a halide salt (e.g., LiF, LiCl, LiBr,
MgCl.sub.2, NaI). The electrolyte can comprise a mixture of salts
(e.g., 25:55:20 mol % LiF:LiCl:LiBr, 50:37:14 mol % LiCl:LiF:LiBr,
etc.). The cell with a Type 2 chemistry can include a molten metal
positive electrode comprising one or more transition metals. In
some cases, the positive electrode comprises zinc (Zn), cadmium
(Cd) and mercury (Hg) or combination thereof, or such material(s)
in combination with other metals, metalloids or non-metals, such
as, for example, a Zn--Sn alloy, Zn--Sn alloy, Cd--Sn alloy, Zn--Pb
alloy, Zn--Sb alloy, or Bi. In an example, the positive electrode
can comprise 15:85, 50:50, 75:25 or 85:15 mol % Zn:Sn.
[0126] In some examples, the electrolyte may comprise two or more
phases. In some cases, formation of an additional phase (e.g., a
solid phase or a second liquid phase) may suppress species
cross-over (e.g., Zn.sup.2+ containing salt crossing over from near
the positive electrode to the negative electrode). Phase separation
may result in formation of inter-salt compounds (e.g. compounds
formed from of ZnCl.sub.2 and LiCl, etc.). In one example,
operating temperature can be reduced to suppress Zn.sup.2+
solubility in a Li-halide salt phase in contact with the negative
electrode (e.g., phase formed due to stratification of two
electrolyte phases). Solubility of Zn metal in Li-halide salts may
be negligible in some cases. In another example, a solid Zn-halide
salt can be formed adjacent to (e.g., in the vicinity of or in
contact with) the positive electrode. In yet another example,
viscosity of the electrolyte salt can be increased to suppress
thermally driven convection of given species (e.g., salt comprising
Zn-halide) toward the negative electrode (e.g., vertically upward
to the negative electrode). The electrolyte may comprise salts of
the positive electrode species. Such salts may be formed as the
positive electrode species dissolves into the electrolyte (e.g.,
during charging). In some cases, such salts (e.g., ZnCl.sub.2) may
suppress a melting point of the electrolyte.
[0127] In some cases, a Type 2 cell can operate at a voltage of at
least about 0.5 V, 1 V, 1.5 V, 2 V, 2.5 V, or 3 V in a charged
state. In some cases, a Type 2 cell can have an open circuit
voltage (OCV) of at least about 0.5 V, 1 V, 1.5 V, 2 V, 2.5 V, or 3
V. In an example, a Type 2 cell has an open circuit voltage greater
than about 1 V, greater than about 2 V, or greater than about 3 V.
In some cases, a charge cutoff voltage of a Type 2 cell is from
about 1 V to 3 V, 1.5 V to 2.5 V, 1.5 V to 3 V, or 2 V to 3 V in a
charged state. In some cases, a charge cutoff voltage (CCV) of a
Type 2 cell is at least about 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V,
1.5 V, 1.6 V, 1.7 V, 1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4
V, 2.5 V, 2.6 V, 2.7 V, 2.8 V, 2.9 V or 3.0 V. In an example, a
Type 2 cell has a charge cutoff voltage of at least about 1.7 V
after at least about 100 charge/discharge cycles. The operating
voltage of a Type 2 cell can be from about 1 V to 2 V, 1 V to 3 V,
1.5 V to 2.5 V, 1.5 V to 3 V, or 2 V to 3 V in a charged state. A
Type 2 cell can provide such voltage(s) (e.g., voltage, OCV and/or
CCV) upon operating at up to and exceeding about 10 cycles, 20
cycles, 30 cycles, 40 cycles, 50 cycles, 100 cycles, 200 cycles,
300 cycles, 400 cycles, 500 cycles, 600 cycles, 700 cycles, 800
cycles, 900 cycles, 1000 cycles, 2000 cycles, 3000 cycles, 4000
cycles, 5000 cycles, 10,000 cycles, 20,000 cycles, 50,000 cycles,
100,000 cycles, 1000,000 or more cycles. In some cases, the
limiting factor on the number of cycles may be dependent on, for
example, the housing and/or the seal as opposed to the chemistry of
the negative electrode, electrolyte and/or the positive electrode.
The limit in cycles may be dictated not by the electrochemistry,
but by the degradation of non-active components of the cell, such
as the container or seal. A cell can be operated without a
substantial decrease in capacity. The operating lifetime of a cell
can be limited, in some cases, by the life of the container, seal
and/or cap of the cell.
[0128] A Type 2 cell may have various advantages. For instance, a
Type 2 cell may include one or more elements that are more abundant
and readily accessible. A Type 2 cell may be less hazardous and
toxic than other chemistries. In addition, some Type 2 chemistries
can have valence states that help avoid, or minimize, oxidization
and/or reduction ("redox") shuttling reactions which can reduce
Coulombic efficiency. In some examples, the positive electrode can
comprise a metal or metalloid that has only one stable oxidation
state (e.g., a metal with a single or singular oxidation state).
For example, the positive electrode (e.g., the active material in
the positive electrode) may comprise a Group 12 element, such as
zinc and/or cadmium, which may only exhibit a single valence state
compared to transition metals (e.g., iron, cobalt, nickel) or
metalloids (e.g., lead, antinomy). In some examples, the positive
electrode may comprise a Group 12 element with a singular stable
oxidation state (e.g., Zn or Cd). In some examples, the positive
electrode may comprise a transition metal with a singular stable
oxidation state. A Type 2 cell of the present disclosure can have
an energy storage capacity of at least about 1 Wh, 5 Wh, 25 Wh, 50
Wh, 100 Wh, 500 Wh, 1 kWh, 1.5 kWh, 2 kWh, 3 kWh, 5 kWh, 10 kWh, 15
kWh, 20 kWh, 30 kWh, 40 kWh, or 50 kWh, and a current density of at
least about 10 mA/cm.sup.2, 20 mA/cm.sup.2, 30 mA/cm.sup.2, 40
mA/cm.sup.2, 50 mA/cm.sup.2, 60 mA/cm.sup.2, 70 mA/cm.sup.2, 80
mA/cm.sup.2, 90 mA/cm.sup.2, 100 mA/cm.sup.2, 200 mA/cm.sup.2, 300
mA/cm.sup.2, 400 mA/cm.sup.2, 500 mA/cm.sup.2, 600 mA/cm.sup.2, 700
mA/cm.sup.2, 800 mA/cm.sup.2, 900 mA/cm.sup.2, 1 A/cm.sup.2, 2
A/cm.sup.2, 3 A/cm.sup.2, 4 A/cm.sup.2, 5 A/cm.sup.2, or 10
A/cm.sup.2.
[0129] Type 2 cells can have cell configurations and be included in
energy storage systems of the present disclosure. A Type 2 cell can
be provided in an energy storage device comprising at least 1, 2,
3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200,
300, 400, 500, 1000, 10,000, 20,000, 50,000, 100,000, 500,000, or
1,000,000 cells, which may be Type 2 cells or a combination of Type
1 cells and Type 2 cells (e.g., 50% Type 1 cells and 50% Type 2
cells). Such cells can be operated under Type 2 mode. In some
cases, a first portion of the cells may be operated in Type 1 mode,
and a second portion of the cells may be operated in Type 2
mode.
[0130] In an example, a Type 2 cell comprises Li.parallel.Zn. In a
charged state, the Li.parallel.Zn cell can have a cell voltage of
at least about 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V, 1.5 V, 1.6 V, 1.7
V, 1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, 2.6 V,
2.7 V, 2.8 V, 2.9 V, or 3.0 V. In an example, the Li.parallel.Zn
cell has an OCV of about 1.86 V. A Li.parallel.Zn cell can be
operated at a temperature of at least about 200.degree. C.,
250.degree. C., 300.degree. C., 350.degree. C., 400.degree. C.,
450.degree. C., 500.degree. C., 600.degree. C., 700.degree. C.,
800.degree. C., or 900.degree. C. In such a case, the negative
electrode, electrolyte and positive electrode are in a liquid (or
molten) state.
[0131] In an example, a Type 2 cell comprises Na.parallel.Zn. In a
charged state, the Na.parallel.Zn cell can have a cell voltage of
at least about 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V, 1.5 V, 1.6 V, 1.7
V, 1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, 2.6 V,
2.7 V, 2.8 V, 2.9 V, or 3.0 V. In an example, the Na.parallel.Zn
cell has an OCV of about 1.6 V. A Na.parallel.Zn cell can be
operated at a temperature of at least about 100.degree. C.,
150.degree. C., 200.degree. C., 250.degree. C., 300.degree. C.,
350.degree. C., 400.degree. C., 450.degree. C., 500.degree. C.,
600.degree. C., 700.degree. C., 800.degree. C., or 900.degree. C.
In such a case, the negative electrode, electrolyte and positive
electrode are in a liquid (or molten) state.
[0132] In another example, a Type 2 cell comprises
Li.parallel.Zn-Sn. Here, Sn can be added to reduce the melting
point of the positive electrode and reduce the activity of Zn in
the positive electrode, which can provide a driving force for
removing Zn droplets that may form in the electrolyte. In a charged
state, the Li.parallel.Zn-Sn cell can have a cell voltage of at
least about 1.2 V, 1.3 V, 1.4 V, 1.5 V, 1.6 V, 1.7 V, 1.8 V, 1.9 V,
2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, 2.6 V, 2.7 V, 2.8 V, 2.9
V, or 3.0 V. A Li.parallel.Zn-Sn cell can be operated at a
temperature of at least about 200.degree. C., 250.degree. C.,
300.degree. C., 350.degree. C., 400.degree. C., 450.degree. C.,
500.degree. C., 600.degree. C., 700.degree. C., 800.degree. C., or
900.degree. C. In such a case, the negative electrode, electrolyte
and positive electrode are in a liquid (or molten) state.
[0133] In another example, a Type 2 cell comprises
Na.parallel.Zn-Sn. In a charged state, the Na.parallel.Zn-Sn cell
can have a cell voltage of at least about 1.2 V, 1.3 V, 1.4 V, 1.5
V, 1.6 V, 1.7 V, 1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V,
2.5 V, 2.6 V, 2.7 V, 2.8 V, 2.9 V, or 3.0 V. A Na.parallel.Zn-Sn
cell can be operated at a temperature of at least about 100.degree.
C., 150.degree. C., 200.degree. C., 250.degree. C., 300.degree. C.,
350.degree. C., 400.degree. C., 450.degree. C., 500.degree. C.,
600.degree. C., 700.degree. C., 800.degree. C., or 900.degree. C.
In such a case, the negative electrode, electrolyte and positive
electrode are in a liquid (or molten) state.
[0134] Energy Storage Systems
[0135] Also provided herein are control systems including computers
programmed to control an energy storage system of the disclosure.
An energy storage system can include an electrochemical energy
storage device with one or more electrochemical energy storage
cells. The device can be coupled to a computer system that
regulates the charging and discharging of the device. The computer
system can include one or more computer processors and a memory
location coupled to the computer processor. The memory location
comprises machine-executable code that, upon execution by the
computer processor, implements any of the methods above or
elsewhere herein.
[0136] In some implementations, an electrochemical energy storage
system comprises at least a first electrochemical cell adjacent to
a second electrochemical cell. Each of the first and second
electrochemical cells can comprise a negative current collector,
negative electrode, electrolyte, positive electrode and a positive
currently collector, where at least one of the negative electrode,
electrolyte and positive electrode are in a liquid state at an
operating temperature of the first or second electrochemical cell.
A positive current lead of the first electrochemical cell can be
directly metal-to-metal joined (e.g., brazed or welded) to the
negative current lead of the second electrochemical second cell. In
some cases, the first and second electrochemical cells are not
connected by wires.
[0137] FIG. 5 shows a system 500 programmed or otherwise configured
to control or regulate one or more process parameters of an energy
storage system of the present disclosure. The system 500 includes a
computer server ("server") 501 that is programmed to implement
methods disclosed herein. The server 501 includes a central
processing unit (CPU, also "processor" and "computer processor"
herein) 505, which can be a single core or multi core processor, or
a plurality of processors for parallel processing. The server 501
also includes memory 510 (e.g., random-access memory, read-only
memory, flash memory), electronic storage unit 515 (e.g., hard
disk), communication interface 520 (e.g., network adapter) for
communicating with one or more other systems, and peripheral
devices 525, such as cache, other memory, data storage and/or
electronic display adapters. The memory 510, storage unit 515,
interface 520 and peripheral devices 525 are in communication with
the CPU 505 through a communication bus (solid lines), such as a
motherboard. The storage unit 515 can be a data storage unit (or
data repository) for storing data. The server 501 can be
operatively coupled to a computer network ("network") 530 with the
aid of the communication interface 520. The network 530 can be the
Internet, an internet and/or extranet, or an intranet and/or
extranet that is in communication with the Internet. The network
530 in some cases is a telecommunication and/or data network. The
network 530 can include one or more computer servers, which can
enable distributed computing, such as cloud computing. The network
530, in some cases with the aid of the server 501, can implement a
peer-to-peer network, which may enable devices coupled to the
server 501 to behave as a client or a server. The server 501 can be
coupled to an energy storage system 535 either directly or through
the network 530.
[0138] The system 500 may comprise a battery management system that
is operatively coupled to the energy storage system 535 through,
for example, a ballasting member (e.g., electronics designed to
balance the electrochemical state-of-charge of cells or cell
modules in a series string). The battery management system can be
implemented, for example, at the server 501. The ballasting member
can include one or more ballasting lines, which can include sensing
lines and current flow lines. The ballasting member can be used to
divert at least some of the current through the cells through the
ballasting member, which can aid in cell balancing. The sensing
lines can be configured to enable the battery management system to
sense, for example, operating temperature and voltage of one or
more cells of the energy storage device of the energy storage
system 535. In some implementations, the sensing lines can be
non-current carrying lines. The battery management system may
comprise a management system board. The battery management system
board can have data acquisition capabilities. For example, the
battery management system board can include a data acquisition
board. The battery management system board may be able to store
and/or process data (e.g., the acquired data). For example, the
battery management system board may be able to store and/or process
the data rather than (or in addition to) converting inputs into
digital signals.
[0139] The storage unit 515 can store process parameters of the
energy storage system 535. The process parameters can include
charging and discharging parameters and operational parameters
based on values of various ballasting members (e.g., sensing lines,
ballasting lines). The server 501 in some cases can include one or
more additional data storage units that are external to the server
501, such as located on a remote server that is in communication
with the server 501 through an intranet or the Internet.
[0140] The server 501 can communicate with one or more remote
computer systems through the network 530. In the illustrated
example, the server 501 is in communication with a remote computer
system 540. The remote computer system 540 can be, for example, a
personal computers (e.g., portable PC), slate or tablet PC (e.g.,
Apple.RTM. iPad, Samsung.RTM. Galaxy Tab), telephone, Smart phone
(e.g., Apple.RTM. iPhone, Android-enabled device, Blackberry.RTM.),
or personal digital assistant.
[0141] In some situations, the system 500 includes a single server
501. In other situations, the system 500 includes multiple servers
in communication with one another through an intranet and/or the
Internet.
[0142] Methods as described herein can be implemented by way of
machine (or computer processor) executable code (or software)
stored on an electronic storage location of the server 501, such
as, for example, on the memory 510 or electronic storage unit 515.
During use, the code can be executed by the processor 505. In some
cases, the code can be retrieved from the storage unit 515 and
stored on the memory 510 for ready access by the processor 505. In
some situations, the electronic storage unit 515 can be precluded,
and machine-executable instructions are stored on memory 510.
Alternatively, the code can be executed on the second computer
system 540.
[0143] The code can be pre-compiled and configured for use with a
machine have a processer adapted to execute the code, or can be
compiled during runtime. The code can be supplied in a programming
language that can be selected to enable the code to execute in a
pre-compiled or as-compiled fashion.
[0144] Aspects of the systems and methods provided herein, such as
the server 501, can be embodied in programming. Various aspects of
the technology may be thought of as "products" or "articles of
manufacture" typically in the form of machine (or processor)
executable code and/or associated data that is carried on or
embodied in a type of machine readable medium. Machine-executable
code can be stored on an electronic storage unit, such memory
(e.g., read-only memory, random-access memory, flash memory) or a
hard disk. "Storage" type media can include any or all of the
tangible memory of the computers, processors or the like, or
associated modules thereof, such as various semiconductor memories,
tape drives, disk drives and the like, which may provide
non-transitory storage at any time for the software programming.
All or portions of the software may at times be communicated
through the Internet or various other telecommunication networks.
Such communications, for example, may enable loading of the
software from one computer or processor into another, for example,
from a management server or host computer into the computer
platform of an application server. Thus, another type of media that
may bear the software elements includes optical, electrical and
electromagnetic waves, such as used across physical interfaces
between local devices, through wired and optical landline networks
and over various air-links. The physical elements that carry such
waves, such as wired or wireless links, optical links or the like,
also may be considered as media bearing the software. As used
herein, unless restricted to non-transitory, tangible "storage"
media, terms such as computer or machine "readable medium" refer to
any medium that participates in providing instructions to a
processor for execution.
[0145] Hence, a machine readable medium, such as
computer-executable code, may take many forms, including but not
limited to, a tangible storage medium, a carrier wave medium or
physical transmission medium. Non-volatile storage media include,
for example, optical or magnetic disks, such as any of the storage
devices in any computer(s) or the like, such as may be used to
implement the databases, etc. shown in the drawings. Volatile
storage media include dynamic memory, such as main memory of such a
computer platform. Tangible transmission media include coaxial
cables; copper wire and fiber optics, including the wires that
comprise a bus within a computer system. Carrier-wave transmission
media may take the form of electric or electromagnetic signals, or
acoustic or light waves such as those generated during radio
frequency (RF) and infrared (IR) data communications. Common forms
of computer-readable media therefore include for example: a floppy
disk, a flexible disk, hard disk, magnetic tape, any other magnetic
medium, a CD-ROM, DVD or DVD-ROM, any other optical medium, punch
cards paper tape, any other physical storage medium with patterns
of holes, a RAM, a ROM, a PROM and EPROM, a FLASH-EPROM, any other
memory chip or cartridge, a carrier wave transporting data or
instructions, cables or links transporting such a carrier wave, or
any other medium from which a computer may read programming code
and/or data. Many of these forms of computer readable media may be
involved in carrying one or more sequences of one or more
instructions to a processor for execution.
[0146] Various parameters of an energy storage system can be
presented to a user on a user interface (UI) of an electronic
device of the user. Examples of UI's include, without limitation, a
graphical user interface (GUI) and web-based user interface. The UI
(e.g., GUI) can be provided on a display of an electronic device of
the user. The display can be a capacitive or resistive touch
display. Such displays can be used with other systems and methods
of the disclosure.
[0147] Interconnections
[0148] Wired or wire-less (e.g., direct metal-to-metal)
interconnections may be formed between individual electrochemical
cells and/or between groups of electrochemical cells (e.g.,
modules, towers, packs, trays, cores, CEs, systems, or any other
group comprising one or more electrochemical cells). In some cases,
groups of cells may be joined via one or more cell-to-cell
interconnections. In some cases, groups of cells may be joined via
a group-level interconnection. The group-level interconnection may
further comprise one or more interconnections with one or more
individual cells of the group. The interconnections may be
structural and/or electrical. Cells and/or groups of cells may be
assembled (or stacked) horizontally or vertically. Such assembled
cells and/or groups of cells may be arranged in series or parallel
configurations. Further, groups of cells may be supported by
various frames. The frames may provide structural support and/or
participate or aid in forming the interconnections (e.g., frames on
groups of cells may mate or be connected).
[0149] In some implementations, interconnections may be configured
to decrease resistance (e.g., internal resistance) in a system
(e.g., a battery). A battery with a low system resistance (e.g.,
such that the battery is capable of efficiently storing energy and
delivering power) may be desirable in some cases. The system
resistance can be determined by the combined effect of a plurality
of resistances along the current flow path such as between
electrochemical cells, within electrochemical cells, and between
groups of electrochemical cells. In some cases, electrochemical
cells or groups thereof are connected using interconnects. In some
instances, an interconnect is a wire. However, the shortest
possible electrical connection can generally lead to the lowest
system resistance. Therefore, the present disclosure describes
direct connection of cells to each other (e.g., by brazing), in
some cases reducing or eliminating the use of wires to connect
electrochemical cells.
[0150] In some implementations, a battery comprises a plurality of
electrochemical cells connected in series, where the battery is
capable of storing at least about 10 kWh of energy, the battery has
an operating temperature of at least about 250.degree. C., and each
of the electrochemical cells has at least one liquid metal
electrode. The battery can be any suitable size. In some cases, the
battery is capable of storing at least about 10 kilo-Watt-hours of
energy. In some cases, the battery is capable of storing at least
about 30 kilo-Watt-hours of energy. In some cases, the battery is
capable of storing at least about 100 kilo-Watt-hours of
energy.
[0151] The internal resistance of the battery can be any suitably
low resistance. In some cases, the internal resistance of the
battery (e.g., at the operating temperature) is about 2.5*n*R,
where `n` is the number of series connected modules of the battery
and `R` (also referred to herein as `R.sub.Module`) is the
resistance of each of the individual modules or parallel connected
modules. In some examples, R is the inverse of the sum of the
inverses of the resistance of each electrochemical cell in a given
module, as given by, for example,
1/R.sub.Module=.SIGMA..sub.i=1.sup.m 1/R.sub.i, where `m` is the
number of cells in one module. Each module can include a plurality
of electrochemical cells in a parallel configuration.
Electrochemical cells in adjacent modules can be arranged in a
series configuration (e.g., individual cells in a module can be
connected in series with corresponding individual cells in an
adjacent module, such as, for example, in a configuration where
individual cells of a first module are connected in series with
individual cells of a second module located above the first
module). In some cases, the internal resistance of the battery
(e.g., at the operating temperature) is about 2*n*R, about 1.5*n*R,
about 1.25*n*R, or about 1.05*n*R. In some cases, the internal
resistance of the battery (e.g., at the operating temperature) is
less than about 2.5*n*R, less than about 2*n*R, less than about
1.5*n*R, less than about 1.25*n*R, or less than about 1.05*n*R. In
some cases, the total system resistance (e.g., at the operating
temperature) is greater than about 1.0*n*R due to the resistance
contribution of interconnects, busbars, surface contact resistance
at connection interfaces, etc. The battery can comprise
electrochemical cells connected in series and in parallel. The
number of electrochemical cell modules (or parallel connected
modules) that are connected in series (i.e., n) can be any suitable
number. In some examples, n is at least 3, at least 5, at least 6,
at least 10, at least 12, at least 15, at least 16, at least 20, at
least 32, at least 48, at least 54, at least 64, at least 108, at
least 128, at least 216, or at least 256. In an example, n is 3
(e.g., for a battery comprising a pack), 6 (e.g., for a battery
comprising a pack), or 216 (e.g., for a battery comprising a
core).
[0152] In some cases, the electrochemical cells are not connected
with wires. In some examples, series connections (e.g., wire-less
cell-to-cell connections) are created with a connection that has an
internal resistance of about 0.5 milliohm (mOhm), about 1 mOhm,
about 2 mOhm, about 5 mOhm, about 10 mOhm, about 50 mOhm, about 100
mOhm, or about 500 mOhm at an operating temperature greater than
250.degree. C. In some examples, series connections are created
with a connection that has an internal resistance of less than
about 0.5 mOhm, less than about 1 mOhm, less than about 2 mOhm,
less than about 5 mOhm, less than about 10 mOhm, less than about 50
mOhm, less than about 100 mOhm, or less than about 500 mOhm at an
operating temperature greater than about 250.degree. C. In some
instances, the resistance is measured by a direct electrical
connection between the conductor of a first electrochemical cell
and the electrically conducting housing of a second cell. Any
aspects of the disclosure described in relation to internal
resistance of cell-to-cell series connections may equally apply to
series connections between groups of cells at least in some
configurations.
[0153] In some implementations, an electrochemical energy storage
system comprises at least a first electrochemical cell adjacent to
a second electrochemical cell, each of the first and second
electrochemical cells comprising a negative current collector,
negative electrode, electrolyte, positive electrode and a positive
currently collector. The negative electrode, electrolyte and
positive electrode can be in a liquid state at an operating
temperature of the first or second electrochemical cell. A positive
current collector of the first electrochemical cell can be direct
metal-to-metal joined (e.g., brazed) to the negative current
collector of the second electrochemical second cell. In some
examples, the negative current collector comprises a negative
current lead.
[0154] In some cases, the first and second electrochemical cells
are not connected by wires. In some cases, the electrochemical
energy storage system comprises one or fewer interconnects for
every 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or more
electrochemical cells. In some cases, the electrochemical energy
storage system (e.g., battery) comprises one interconnect for at
least every 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50,
75, 100, 150, 200, or more electrochemical cells.
[0155] FIG. 6 shows an example of a cell pack 600 comprising 3
modules 605. Each of the modules comprises 12 cells 630 that are
connected in parallel 610. The modules are held in place with cell
pack framing (also "frame" herein) 615 that includes a top
component of the frame 620. The cells are stacked directly on top
of each other with the negative current terminal of one cell 625
contacted directly with the housing of another cell (e.g., the cell
above it). The negative current terminals of the top layer of cells
can have no housing of another cell directly above, so can instead
be contacted (e.g., brazed to) a negative busbar 635.
[0156] In some configurations, the parallel connections 610 made in
the module can be created using a single piece (or component) with
multiple pockets for cell materials. This piece can be a stamped
component that allows for direct electrical connection between
cells. In some examples, the stamped pocketed electrically
conductive housing does not create a barrier between the cells. In
some cases, the pocketed electrically conductive housing seals the
pockets from each other. This electrically conductive housing can
be easier to manufacture and assemble than individual electrically
conductive cell housings.
[0157] When stacked vertically, the electrochemical cells bear the
weight of the cells stacked above. The cells can be constructed to
support this weight. In some cases, cell-to-cell spacers 640 are
placed between the layers of cells. These spacers can disperse the
weight of the above cells and/or relieve some of the weight applied
to the negative current terminals. In some cases, the negative
current terminals are electrically isolated from the housing with a
seal. This seal can be the weakest structural component of the
electrochemical cell, so the spacers can reduce the amount of force
applied to the seals.
[0158] In some implementations, a liquid metal battery comprises a
plurality of electrochemical cells each comprising an electrically
conductive housing and a conductor in electrical communication with
a current collector. The electrically conductive housing can
comprise a negative electrode, electrolyte and positive electrode
that are in a liquid state at an operating temperature of the cell.
The conductor can protrude through the electrically conductive
housing through an aperture in the electrically conductive housing
and can be electrically isolated from the electrically conductive
housing with a seal. The plurality of electrochemical cells can be
stacked in series with the conductor of a first cell in electrical
contact with the electrically conductive housing of a second cell.
The liquid metal battery can also comprise a plurality of
non-gaseous spacers disposed between the electrochemical cells. In
some cases, the electrochemical cells are stacked vertically. For
example, at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 36,
40, 48, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 216, 250,
256, 300, 350, 400, 450, 500, 750, 1000, 1500, 2000 or more
electrochemical cells can be stacked in series. In some cases, the
battery further comprises at least one additional electrochemical
cell connected in parallel to each of the plurality of
electrochemical cells that are stacked in series. For example, each
vertically stacked cell can be connected in parallel with at least
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 16, 20, 25, 30, 40, 50, 60, 70,
80, 90, 100, 120, 140, 160, 180, 200, 250, 300, 350, 400, 450, 500,
750, 1000, 1500, 2000 or more additional electrochemical cells. In
some cases, the electrically conductive housings are part of a
current conducting pathway.
[0159] The non-gaseous spacers (also "spacers" herein) can be a
solid material. In some cases, the spacers comprise a ceramic
material. Non-limiting examples of ceramic materials include
aluminum nitride (AlN), boron nitride (BN), yttrium oxide
(Y.sub.2O.sub.3), zirconium oxide (ZrO.sub.2), yttria partially
substituted zirconia (YPSZ), aluminum oxide (Al.sub.2O.sub.3),
chalcogenides, erbium oxide (Er.sub.2O.sub.3), silicon dioxide
(SiO.sub.2), quartz, glass, or any combination thereof. In some
cases, the spacers are electrically insulating.
[0160] The spacers can have any suitable thickness. In some cases,
the thickness of the spacer is approximately equal to the distance
that the conductor protrudes through the electrically conductive
housing (e.g., the thickness of the spacer can be within about
0.005%, about 0.01%, about 0.05%, about 0.1% or about 0.5% of the
distance that the conductor protrudes through the electrically
conductive housing).
[0161] The majority of the force (e.g., the weight of
electrochemical cells stacked vertically above a cell) is generally
born by the spacers and/or housing rather than the seals. The
non-gaseous spacers and/or the electrically conductive housing can
support any suitably high percentage of the applied force. In some
cases, about 70%, about 80%, about 90%, about 95%, or about 95% of
the force is applied to the non-gaseous spacers and/or the
electrically conductive housing. In some cases, at least about 70%,
at least about 80%, at least about 90%, at least about 95%, or at
least about 95% of the force is applied to the non-gaseous spacers
and/or the electrically conductive housing.
[0162] There can be any suitable amount of force applied to the
electrically conductive housing and/or seal. In some instances, the
force applied to the seal is no greater than the seal can support.
In some cases, the force applied to the seal is about 10, about 15,
about 20, about 25, about 30, about 35, about 40, about 45, about
50, about 60, about 70, about 80, about 100, about 120, about 150,
or about 200 Newtons. In some cases, the force applied to the seal
is less than about 10, less than about 15, less than about 20, less
than about 25, less than about 30, less than about 35, less than
about 40, less than about 45, less than about 50, less than about
60, less than about 70, less than about 80, less than about 100,
less than about 120, less than about 150, or less than about 200
Newtons. In some cases, the force applied to the housing is about
100, about 500, about 1000, about 5000, or about 10000 Newtons. In
some cases, the force applied to the housing is at least about 100,
at least about 500, at least about 1000, at least about 5000, or at
least about 10000 Newtons.
[0163] There can be any suitable amount of pressure applied to the
electrically conductive housing and/or seal. In some instances, the
pressure applied to the seal is no greater than the seal can
support. In some cases, the pressure applied to the seal is about
1, about 10, about 50, about 100, about 200, about 300, or about
500 pounds per square inch (psi). In some cases, the pressure
applied to the seal is less than about 50, less than about 100,
less than about 200, less than about 300, or less than about 500
pounds per square inch (psi). In some cases, the pressure applied
to the housing is about 500, about 1000, about 2000, about 2500,
about 3000, about 5000, or about 10000 pounds per square inch
(psi). In some cases, the pressure applied to the housing is at
least about 500, at least about 1000, at least about 2000, at least
about 2500, at least about 3000, at least about 5000, or at least
about 10000 pounds per square inch (psi).
[0164] The cell to cell connections can be configured in a variety
of ways based on tolerances and optimal conductive path. In one
configuration, the top face of the negative current lead in one
cell can be direct metal-to-metal joined (e.g., brazed) to the
bottom of the cell above it (see, for example, FIG. 7). Other
configurations include, for example, alternative direct
metal-to-metal join (e.g., alternative braze join) configurations,
such as an outer diameter braze enhanced by differences in the
coefficient of thermal expansion (CTE) of the inner rod and the
outer fixture (see, for example, FIG. 8).
[0165] In some cases, as shown in FIG. 7, the conductor 705 of a
first cell 710 is brazed 715 to the electrically conductive housing
720 of the second cell 725. The braze material can be any suitable
material. Some non-limiting examples of braze materials include
materials that comprise iron (Fe), nickel (Ni), titanium (Ti),
chromium (Cr), zirconium (Zr), phosphorus (P), boron (B), carbon
(C), silicon (Si), or any combination thereof. The cell can
comprise a cathode 730, an electrolyte 735 and an anode 740
connected to the current collector and conductor 705. The conductor
can feed through the cell lid 750. In some cases, the cell has some
empty head space 745.
[0166] In some implementations, the conductor 705 can feed through
a seal 760 in the cell lid 750. The conductor (e.g., negative
current lead) 705 may rigid. The seal 760 may not be rigid. As
additional cells are added during assembly, an increasing weight
can be exerted on the conductor 705 of the bottom cell 710 by the
housing 720 of the top cell 725 (e.g., at the position 715). In
some instances, the vertical spacing between the cells 710 and 725
may decrease if the seal 760 (with the conductor 705 and the anode
740) move downward into the cell 710 as a result of the compression
force. To ensure that modules are electrically isolated from each
other, spacers (e.g., ceramics) 755 can be placed across the
surface of the cells to support the cells above them. In this
configuration, the cell housing can be used as the main structural
support for the system. The ceramic spacer 755 can relieve the seal
760 from having to support the weight of the top cell 725 (and any
additional cells added during assembly). In some configurations,
there may initially be a gap between the top of the spacers 755 and
the bottom of the housing 720 of the top cell 725 (e.g., the
thickness of the spacer can be slightly less than the distance that
the conductor initially protrudes through the electrically
conductive housing), and the spacers (e.g., ceramics) can be placed
in compression during assembly as additional cell(s) are added
(e.g., as the spacing between the top of the housing of the bottom
cell 710 and the bottom of the housing of the top cell 725
decreases). As a result, the displacement (also "anode-cathode
displacement" herein) between anodes and cathodes (e.g., final
displacement after assembly between the anode 740 and the cathode
730 in cell 710) can in some cases be determined by the non-gaseous
spacers. In some configurations, the spacers can be placed in
compression right away (e.g., if the thickness of the spacer is
slightly greater than the distance that the conductor initially
protrudes through the electrically conductive housing).
[0167] In some cases, differences in the coefficient of thermal
expansion (CTE) can be used to connect two cells. As shown in FIG.
8, the conductor of the first cell 805 sits in a recessed portion
of the electrically conductive housing of the second cell 810, and
the coefficient of thermal expansion (CTE) of the conductor 815 is
greater than the CTE of the electrically conductive housing
820.
[0168] The CTE of the conductor can be any amount greater than the
CTE of the electrically conductive housing. In some cases, the CTE
of the conductor is about 2%, about 5%, about 10%, about 15%, or
about 20% greater than the CTE of the electrically conductive
housing. In some cases, the CTE of the conductor is at least about
2%, at least about 5%, at least about 10%, at least about 15%, or
at least about 20% greater than the CTE of the electrically
conductive housing.
[0169] Cells stacked vertically in series can be attached through a
hard electrical connection such that the height from 750 to 740
and/or anode-cathode displacement (ACD) can be determined by the
dimensional tolerance of 755. In some examples, the height from 750
to 740 can be at least about 3 millimeters (mm), at least about 5
mm, at least about 7 mm, at least about 10 mm, at least about 15
mm, and the like. In some examples, the ACD can be about 3 mm,
about 5 mm, about 7 mm, about 10 mm, about 15 mm, or greater. FIG.
7 is an example of how such connections may be configured.
[0170] Cells stacked vertically in series can be connected using a
hard electrical connection such that resistance per cell connection
is reduced, for example, below about 100 mOhm (or another internal
resistance value described elsewhere herein). FIG. 7 is an example
of how such connections may be configured.
[0171] In some implementations, cells can be joined vertically by
means of a current transfer plate that is welded to the negative
current lead or conductor on the bottom cell, and the cell body
(e.g., electrically conductive housing) on the top cell. For
example, multiple cells can be connected in parallel into a cell
module or a partial cell module, and then connected in series with
other cell modules or partial cell modules via vertical stacking.
The vertical stacking can be implemented by connecting the current
transfer plate from one cell to the cell body or a feature on the
cell body on the cell above it (e.g., to form the basis of a cell
pack).
[0172] In some examples, the welded connection can have an internal
resistance of about 0.05 milliohm (mOhm), about 0.1 mOhm, about 0.5
mOhm, about 1 mOhm, about 2 mOhm, about 5 mOhm, about 10 mOhm,
about 50 mOhm, about 100 mOhm, or about 500 mOhm at an operating
temperature greater than 250.degree. C. In some examples, the
series connections can be created with a connection that has an
internal resistance of less than about 0.05 mOhm, less than about
0.1 mOhm, less than about 0.5 mOhm, less than about 1 mOhm, less
than about 2 mOhm, less than about 5 mOhm, less than about 10 mOhm,
less than about 50 mOhm, less than about 100 mOhm, or less than
about 500 mOhm at an operating temperature greater than about
250.degree. C.
[0173] FIG. 13 is a perspective view of an electrochemical cell
1305 with a current transfer plate 1310 connected (e.g., welded) to
a negative current lead 1315. The negative current lead can
protrude through a housing 1320 of the cell 1305 through a seal
(not shown). The current transfer plate can in some instances
comprise a main portion 1325 in contact with the negative current
lead, and one or more other portions 1330. The other portion(s) can
be integrally formed with the main portion. The other portion(s)
can be symmetrically (e.g., coaxially) or asymmetrically placed
with respect to the main portion. For example, the current transfer
plate can comprise a central portion 1325 and one or more flat
elongated portions (e.g., flaps, tongues or tabs) 1330. The current
transfer plate can be formed from a conductive material, such as
any conductive material described herein. The other portion(s) can
comprise a flat surface that can be welded or otherwise direct
metal-to-metal joined with another surface (e.g., a cell body or a
feature on the cell body of an adjacent cell). The current transfer
plate (e.g., the other portion(s), such as the elongated portions
1330) can extend from the negative current lead toward the
periphery of the cell surface comprising the negative current lead.
Such configurations can enable electrical connections to be more
conveniently made in tight spaces between cells or in cell
assemblies. For example, the elongated portions 1330 can be more
conveniently connected (e.g., welded to an adjacent cell body)
during vertical stacking of cells because they can be more
conveniently accessed (e.g., when accessing the cell from a
direction parallel to the surface comprising the negative current
lead, the connection can be made at the periphery of the surface
comprising the negative current lead rather than near the
center).
[0174] The current transfer plate may be combined with or comprise
a strain relieving function to reduce stress on the seal (e.g., the
seal around the negative current lead) that may be generated by the
welding/joining process and/or thermal expansion differences during
heat-up and/or cool-down. In some cases, the stresses on the seal
may be reduced by including an electrically insulating non-gaseous
(e.g., ceramic) spacer. The non-gaseous spacer can support the
weight from the current transfer plate and/or cells stacked onto
the current transfer plate and direct the weight onto the housing
(e.g., the cell cap), thereby reducing the portion of the applied
weight that is transmitted through the seal. In some cases, the
strain relieving function may include a spiral pattern (e.g., a
single spiral arm or multiple spiral arms) or other feature on the
current transfer plate. The spiral pattern may be created by
cutting away and/or removing material from the current transfer
plate in the desired pattern. For example, the spiral feature on
the main portion 1325 can give the current transfer plate
compliance and may reduce stress experienced by the seal as the
cells are stacked on top one another or during heat-up due to CTE
mismatches. The spiral pattern may comprise one or more spiral
arms. The spiral arms may be, for example, about 0.5 mm thick,
about 1 mm thick, about 2 mm thick or about 4 mm thick. The spiral
arms may create a spiral that has a circular or oval external shape
that is about 1 cm, about 2 cm, about 3 cm or about 4 cm or larger
in diameter. In some cases, the current transfer plate may be
sufficiently compliant such that the strain relieving feature is
not needed.
[0175] Cell packs can be attached in series and parallel in various
configurations to produce cores, CEs, or electrochemical systems.
The number and arrangement of various groups of electrochemical
cells can be chosen to create the desired system voltage and energy
storage capacity. The packs, cores, CEs, or systems can then be
enclosed together in high temperature insulation to create a system
that can heat itself using the energy created from cells charging
and discharging. For example, FIG. 9 is an example of how packs can
be configured, indicating that the cell packs in a given plane are
connected to one another in parallel 905, while the packs connected
directly atop one another are connected in series 910.
[0176] The packs themselves can be connected vertically and
horizontally to one another through busbars (e.g., unlike the
cell-to-cell connections within a pack which can generally be
direct connections such as brazes or welds). In some cases, the
busbar is flexible or comprises a flexible section (e.g., to
accommodate non-isothermal expansion of the system throughout heat
up and operation).
[0177] A busbar can be used to make an electrical connection with
cells in a parallel string (e.g., a parallel string of cells, a
parallel string of packs, etc.). In some examples, a busbar can be
used to configure a set of cells or cell modules into a parallel
string configuration by being electrically connected with the same
terminal on all of the cells or cell modules (e.g., the negative
terminals of all of the cells or cell modules, or the positive
terminals of all of the cell or cell modules). For example, a
positive busbar and/or a negative busbar may be used. The positive
busbar can be connected to the housing and may or may not need to
be flexible. In some cases, the positive busbar may not be used.
The negative busbar can be joined to features in (or on) one or
more of the cell bodies (e.g., the cell bodies of individual cells
in a pack) to provide a strong electrical connection. In some
cases, the negative busbar can be attached to conductive
feed-throughs (e.g., negative current leads), which may require
some compliance for thermal expansion. For example, a flexible
connection between a relatively rigid busbar core and the
feed-through may be achieved using a compliance feature between the
feed-through and the busbar. The compliance feature may involve a
spiral pattern (e.g., a single spiral arm or multiple spiral arms)
that may be created by cutting away and/or removing material from a
flat busbar in the desired pattern. The spiral pattern may involve
one or more spiral arms. The spiral arms may be, for example, about
0.5 mm thick, about 1 mm thick, about 2 mm thick or about 4 mm
thick. The spiral arms may create a spiral that has a circular or
oval external shape that is about 1 cm, about 2 cm, about 3 cm or
about 4 cm or larger in diameter. In some cases, the busbar may be
sufficiently compliant such that the compliance feature is not
needed.
[0178] One or more interconnects can be used to connect the busbar
of one pack to the busbar of another cell pack, thereby placing the
cell packs in parallel or in series. In some cases, the negative
busbar of one cell pack is connected to the positive busbar of
another cell pack using a compliant interconnection component (also
"interconnect" herein). In some cases, the interconnect may be
braided metal or metal alloy. In some cases, the interconnect may
be made from sheet metal and take the form of a bent sheet that is
about 1/32 inch thick, about 1/16 inch thick, about 1/8 inch thick,
or about 1/4 inch thick. In some cases, the interconnect may
comprise the same conductive material as the busbar. In some cases,
the positive busbar and the interconnect are the same component
(see, for example, FIG. 14).
[0179] The busbar and/or interconnect components can comprise a
conductive material. In some cases, the busbar and/or interconnect
components can comprise (e.g., be made of) stainless steel or
nickel. In some cases, copper can be used as busbar material (e.g.,
due to its high electrical conductivity of, for example, about
60.times.10.sup.6 S/m at 20.degree. C. and about 20.times.10.sup.6
S/m at 500.degree. C.). For example, copper may be used for high
temperature battery systems that operate at less than about
450.degree. C.; however, above about 450.degree. C., copper may be
oxidized and/or lose structural integrity and may not be suitable
for long-term use in high temperature battery systems. In some
cases, the busbar and/or interconnect can comprise (e.g., be made
from) a material that has a conductivity greater than stainless
steel (e.g., greater than about 2.times.10.sup.6 S/m at 20.degree.
C. or greater than about 1.times.10.sup.6 S/m at 500.degree. C.).
For example, nickel may be used as a busbar and/or interconnect
(e.g., in high temperature batteries) based on its electrical
conductivity, which can be greater than the electrical conductivity
of stainless steel but less conductive than copper.
[0180] In some cases, the busbar and/or interconnect may be made
from an aluminum-copper based alloy that may have a conductivity
similar to nickel but may be less expensive. Examples of such
aluminum-copper based alloy can include, but are not limited to,
aluminum-copper, aluminum-bronze or aluminum-brass, where the
material comprises about 1 weight-percent aluminum (wt %), about 2
wt % aluminum, about 5 wt % aluminum, about 10 wt % aluminum or
about 15 wt % aluminum, with most of the remainder of the material
being copper, bronze or brass. Bronze may comprise, for example,
about 88 wt % copper and about 12% tin, or primarily copper with
other additives and smaller amounts of tin. Brass is a copper-zinc
alloy that may comprise, for example, from about 60 wt % to about
90 wt % copper, from about 20 wt % to about 40 wt % zinc, and from
about 1 wt % to about 20 wt % other materials such as tin, nickel,
iron or lead. In some examples, the material of choice may be a
copper-aluminum alloy comprising about 91 wt % copper, about 7 wt %
aluminum and about 2 wt % iron. In some examples, the material of
choice may be a copper-aluminum alloy comprising about 82 wt %
copper, about 5 wt % nickel, about 2 wt % iron and about 10 wt %
aluminum. The electrical conductivity of such aluminum-copper
alloys at cell operating temperature (e.g., 500.degree. C.) may be
about 2.times.10.sup.6 S/m, about 3.times.10.sup.6 S/m, about
4.times.10.sup.6 S/m, about 5.times.10.sup.6 S/m, about
6.times.10.sup.6 S/m, about 7.times.10.sup.6 S/m, about
8.times.10.sup.6 S/m, about 9.times.10.sup.6 S/m, or about
10.times.10.sup.6 S/m.
[0181] In some cases, the busbar and/or interconnect component
material may comprise (e.g., be made from) copper or a copper alloy
that is coated with an oxidation-resistant material such as, for
example, aluminum, aluminum-bronze, aluminum-brass, chromium,
nickel, stainless steel, or any combination thereof. In some cases,
the busbar and/or interconnect may comprise a copper core with a
jacket or cladding that is oxidation-resistant, such as, for
example, a jacket or cladding comprising aluminum, aluminum-bronze,
aluminum-brass, chromium, nickel, stainless steel, or any
combination thereof. The electrical conductivity of such
coated/jacketed/clad materials may be similar to that of the
substrate. For example, copper or a copper alloy jacketed with
stainless steel can have a conductivity of about 90-100% that of
copper.
[0182] A busbar and/or interconnect made from a non-ferrous alloy
may be joined (e.g., brazed, press-fit or welded) to one or more
end-caps (e.g., stainless steel end-caps) which may then enable the
end-caps of the busbar or interconnect to be more easily joined
(e.g., welded) to the appropriate busbar/interconnect/cells. For
example, an end-cap may be more easily joined to a
busbar/interconnect (e.g., at a first connection point of the
end-cap) and/or to a cell (e.g., at a second connection point of
the end-cap). In some instances, individual end-caps may be
configured to join to both a busbar/interconnect and a cell. In
some instances, separate end-caps may be provided for joining to a
busbar/interconnect and for joining to a cell.
[0183] The busbars can be configured, for example, as shown in FIG.
10. A first cell 1005 is connected in parallel to a second cell
1010 (e.g., by direct contact of their housings). The connection
can comprise a positive busbar 1015 and a negative busbar 1020
separated by a ceramic separator 1025. In some cases, the separator
comprises a ceramic material. Non-limiting examples of ceramic
materials include aluminum nitride (AlN), boron nitride (BN),
yttrium oxide (Y.sub.2O.sub.3), zirconium oxide (ZrO.sub.2), yttria
partially substituted zirconia (YPSZ), aluminum oxide
(Al.sub.2O.sub.3), silicon dioxide (SiO.sup.2), magnesium oxide
(MgO), quartz, glass, or any combination thereof. In some cases,
the separator is electrically insulating.
[0184] In some examples, a connection between any two groups of
cells using one or more busbars and/or interconnects has an
internal resistance of about 0.01 mOhm, about 0.05 mOhm, about 0.1
mOhm, about 0.2 mOhm, about 0.5 mOhm, about 1 mOhm, about 5 mOhm,
about 10 mOhm, about 50 mOhm, or about 100 mOhm. In some examples,
a connection between any two groups of cells using one or more
busbars and/or interconnects has an internal resistance of at least
about 0.01 mOhm, at least about 0.05 mOhm, at least about 0.1 mOhm,
at least about 0.2 mOhm, at least about 0.5 mOhm, at least about 1
mOhm, at least about 5 mOhm, at least about 10 mOhm, at least about
50 mOhm, or at least about 100 mOhm. In an example, an internal
resistance between a first plurality of electrochemical cells and a
second plurality of electrochemical cells connected to a busbar of
the first plurality of electrochemical cells is less than about 10
mOhm or less than about 100 mOhm. In some instances, the resistance
is measured by the voltage drop across the busbar (and/or
interconnect) while current is flowing through the busbar (and/or
interconnect) according to the following formula: R.sub.busbar=V/I,
where `R.sub.busbar` is the resistance of the busbar (and/or
interconnect), `V` is the measured voltage drop across the busbar
(and/or interconnect) and `I` is the current flowing through the
busbar (and/or interconnect).
[0185] The positive and negative busbars may or may not be
separated by a separator. For example, the positive and negative
busbars may be provided on opposing ends of a module, pack, or any
other group of one or more electrochemical cells. In some cases,
the busbars may be physically separated such that a separator is
not needed. In some cases, the busbars may be provided on adjacent
surfaces of a unit (see, for example, FIG. 14) and a separator may
or may not be provided.
[0186] FIG. 14 is an example of a pack 1405 with a first interpack
busbar 1410 (e.g., a negative busbar) and a second interpack busbar
1415 (e.g., a positive busbar). The busbar 1410 may or may not be
separated from the busbar 1415 by a separator (e.g., at interface
1430). The busbars 1410 and/or 1415 may in some instances be used
to connect the pack 1405 to one or more other packs (e.g., in
series or parallel configurations depending on the polarity of the
busbar of the other pack).
[0187] A busbar connected to a first group of electrochemical cells
(e.g., on a pack) may comprise a feature to allow the busbar (and
therefore the first group of cells) to be electrically connected to
a second group of cells (e.g., another pack). For example, the
busbar 1415 or 1410 can comprise a flange, hook, ledge, interlock
feature, weldable tab, brazable tab, snap fit or other member to
allow the busbar to be interconnected with an adjacent group of
cells (e.g., at a connection interface of the adjacent group of
cells, to a busbar of the adjacent group of cells, to an
interconnect on the adjacent group of cells, to an interconnect
between the busbar on the first group of cells and a busbar on the
second (adjacent) group of cells, etc.).
[0188] Busbar(s) may be configured to snap onto, be joined to
(e.g., welded, brazed), or otherwise create a mating connection
with a group of electrochemical cells. For example, the busbar 1415
can have a flange, hook, ledge, interlock feature, snap fit,
weldable feature, brazable feature, bolted connection or other
member that mates with the pack 1405 (e.g., at or near the
interface 1430). For example, the busbar may mate with the pack at
a connection interface. The connection interface may include one or
more walls or housing components of cell(s) in the group of cells.
The group of cells (e.g., a pack) may comprise a corresponding
mating feature. For example, the pack 1405 can comprise a frame
that mates with the busbar (e.g., allowing it to be snapped onto
the pack). The frame may be electrically insulated from the cells,
cell modules, and/or series stack of cell modules. In an example, a
welded or brazed joint can be used. The joint may in some cases be
cut in order to free the pack/interconnect/busbar.
[0189] The pack 1405 may further comprise or form other
interconnections (e.g., to allow the pack 1405 to be interconnected
with additional packs), including, but not limited to, additional
interconnects, additional busbars and/or additional connection
interfaces. For example, the pack 1405 may be further comprise
additional interconnections at surfaces 1420 and/or 1425 (e.g., a
positive interconnect, busbar or interconnection interface for
connecting to another pack positioned adjacent to the surface 1425,
and/or a positive interconnect, busbar or interconnection interface
for connecting to another pack positioned adjacent to the surface
1420). Alternatively, one or more of the interconnections 1410
and/or 1415 may wrap around the pack 1405. For example, the
positive busbar 1415 may further extend to the surface 1420, or to
both the surface 1420 and the surface 1425. In another example, the
negative busbar 1410 may further extend to the surface 1425, or to
both the surface 1425 and the surface 1420. In some
implementations, busbars may be used to provide pack-level
electrical connections/interconnections (e.g., only busbars may be
used for pack-level electrical connections/interconnections).
[0190] In configurations where cells are stacked vertically atop
one another, the busbar at the top of the cell stack (e.g., cell
pack stack) can comprise only the negative busbar (e.g., since the
positive terminal of the stack can be on the bottom cell in the
stack).
[0191] The core may be designed with multiple packs electrically
connected in series and/or in parallel. The packs that are part of
the core may be contained (e.g., all contained) within a single
thermally managed chamber. For example, thermal insulation may
surround a set of packs, thus keeping the packs (e.g., all packs)
in good thermal contact with each other and thermally insulating
the packs (e.g., all of the packs) from ambient conditions. In some
cases, the core comprises electrically powered heaters installed
near an inner surface of at least a portion of the insulation,
electrically powered heaters distributed throughout the internal
heated zone and/or connected to cell packs, or a combination
thereof.
[0192] In some cases, the packs are arranged on trays that are
arranged in a vertical stack. In some cases, the packs may be
arranged on trays that are arranged in a horizontal stack. A
plurality of trays (e.g., 2, 3, 4, 5, 10, 15, 20, 25, 30 or more
trays) can be assembled into a core. The trays can be supported
with an internal metal frame in the core. The packs can be
assembled on each tray. The tray can provide mechanical support for
the packs. The tray can be electrically isolated from the cells in
the cell packs that are arranged on the tray. The packs in each
tray can be series and/or parallel connected. The packs in each
tray may be connected horizontally and/or vertically. In one
example, the packs are assembled on each tray in a configuration
about 1 pack deep and about 6 packs across. In another example, the
packs are assembled on each tray in a configuration about 2 packs
deep and about 4 packs across. In some cases, the packs are only
connected in series to increase the core voltage. In some cases,
two or more packs are stacked directly on top each another on one
tray, with one or more trays within the core. Some of the packs on
adjacent trays may be connected to each other to provide series
connections between trays. Further, in some cases, some of the
packs on adjacent trays may be connected to each other to provide
parallel connections between trays. In some examples, the packs
comprise about 6 modules stacked vertically on top each another and
are about 1 cell wide and about 6 cells deep. In some examples, the
packs comprise about 3 modules stacked vertically on top one
another and are about 2 cells wide and about 8 cells deep.
[0193] The thermal insulation and/or the frame may be designed to
allow the core (and/or any system of the disclosure) to be cooled,
the insulation to be removed, a tray to be disconnected and removed
from the core to allow for a single pack to be disconnected,
removed and replaced, or any combination thereof. The core can then
be reassembled and heated back up to operating temperature to allow
for resumed operation.
[0194] The battery can have interconnects (e.g., wires) in addition
to direct metal-to-metal joints (e.g., welds and brazes). A balance
can be struck between the number of interconnects and the number of
direct metal-to-metal joints where there are enough direct
metal-to-metal joints to achieve a suitably low system resistance,
but not so many that an entire battery is rendered inoperable and
cannot be repaired without destroying direct metal-to-metal joints
should one or more electrochemical cells fail. For example,
interconnects may be advantageously used to enable modular assembly
of the battery (e.g., module interchanges). Flexible interconnects
can be used to reduce stresses generated between groups of cells
(e.g., between cell packs) due to thermal gradients and differences
in the coefficient of thermal expansion of components in the groups
of cells (e.g., cell packs) and busbars (and/or other
interconnections).
[0195] In some cases, the battery comprises at least one
electrochemical cell connected in parallel with a plurality of
electrochemical cells that are then stacked in series. The parallel
connections can be made by creating the electrically conductive
housing for multiple cells from one manufactured part. The housings
can be stamped from a continuous piece of metal for example. In
some cases, the parallel connections are formed by interconnects
that allow at least some of the electrochemical cells comprising
the battery to be replaced without breaking a direct metal-to-metal
joint. In some cases, the parallel connections are formed by
welding together cell bodies of adjacent cells (e.g., welding
together the corners of adjacent cell bodies by melting together
material from the cell body of adjacent cells and/or adding and
melting filler material to the weld joint). In some cases, welding
cell bodies directly to one another may risk creation of a hole in
the cell body that may compromise the performance of the cell(s).
To avoid the risk of creating a hole in the cell body, features may
be added to the cell body (e.g., integrally formed with a housing
or cell body, welded to the cell body during manufacturing, etc.)
of one or more of the cells to be joined to allow the parallel
connections to be formed by welding together the features in cell
bodies of adjacent cells (e.g., welding together one or more tabs
that stick out from the cell body and are positioned to be adjacent
one or more tabs in an adjacent cell). One or more features (e.g.,
tabs, flanges, hooks, ledges or other weldable or brazable
features) in the cell body may be provided on at least one of the
cells to be joined. In some cases, one or more features in the cell
body may be provided on all of the cells to be joined. The features
may be positioned (e.g., aligned) to facilitate the formation of
the parallel connection (e.g., to allow the features to be
welded).
[0196] The battery can include a common single point connector.
Multiple wires (e.g., ends of the wires) can be connected to the
common single point connector (i.e., several wires can be connected
to a common connector, which can connect to other portions of the
battery at a single point).
[0197] In some implementations, a liquid metal battery can comprise
a plurality of electrochemical cells connected in series and
parallel. Each of the electrochemical cells can comprise a negative
electrode, an electrolyte and a positive electrode. At least one of
the negative electrode, the electrolyte and the positive electrode
can be in a liquid state at an operating temperature of the
electrochemical cell(s). The liquid metal battery can include a
plurality of wires having a first end and a second end. The first
end can be connected to at least one of the electrochemical cells
(e.g., directly or indirectly). In some cases, the first end can be
connected to a common single point connector, and the common single
point connector can be connected to at least one of the
electrochemical cells (e.g., to a busbar, to a cell body, to a
feature in a cell body such as a tab protruding from the cell body,
etc.). The second end can be connected, for example, to control
circuitry (e.g., directly or indirectly) or to another common
single point connector. In some cases, the second end can be
connected to a common single point connector, and the common single
point connector can be connected to control circuitry. For example,
the single point connector on the second end (or the second end
itself) can be connected to control circuitry located outside the
thermally insulated zone containing cell packs, such as, for
example, to a battery management system (e.g., to a battery
management system board). In some cases, the first ends of a set of
wires can be connected to a single point connector, the second ends
of a subset of the wires can be connected to another single point
connector, and the remaining wire or wires (e.g., the remaining
second ends of the wires) can be separately connected to another
part of the battery (e.g., voltage sense line input port of a
battery management system).
[0198] In some implementations, the single point connector forms an
electrical connection with another plurality (group) of
electrochemical cells (e.g., to connect together modules, packs,
cores, CEs, or systems).
[0199] An adapter plate can create a single point connection for
multiple wires to a busbar in a module, pack, core, or CE. The
wires can be welded or brazed to the back of the adapter plate to
facilitate single point separation of a large quantity of wires
connecting to a busbar. In order to effectively balance and monitor
cells within a cell module, multiple wire connections may need to
be created. The connection point can be a potential point of
failure and can add to the cost and complexity of assembly. In some
implementations, a terminal that has the wires connected to it can
be pre-fabricated. The plate can be bolted, welded or brazed
wherever the connection is required. Wires connected in this manner
can remain static through many uses and disconnections, thus
reducing wire wear-tear and embrittlement effects. Thus, single
point connectors can in some cases enable more facile module
interchanges.
[0200] In some implementations, the first end of the wire is
connected to a busbar that is in electrical communication with at
least one of the electrochemical cells. FIG. 11 shows an example of
a cell module (e.g., in a pack comprising a single module) with
busbars and wires. The module includes handles 1105, in this case
for lifting twelve electrochemical cells 1110 arranged in a 3 by 4
cell array. The electrochemical cells can be in electrical
communication with a negative busbar 1115 and a positive busbar
1120. One or more ceramic spacers 1125 can be used to displace
weight from the seals. The wires can be connected to common single
point connectors (e.g., a negative single point connector 1130 and
a positive single point connector 1135).
[0201] Any number of wires can be connected to a common single
point connector. In some examples, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 35, or
40 wires are connected to the single point connector. In some
cases, at least 1, at least 2, at least 3, at least 4, at least 5,
at least 6, at least 7, at least 8, at least 9, at least 10, at
least 11, at least 12, at least 13, at least 14, at least 15, at
least 16, at least 17, at least 18, at least 19, at least 20, at
least 22, at least 24, at least 26, at least 28, at least 30, at
least 35, or at least 40 wires are connected to the single point
connector.
[0202] FIG. 12 shows an example of a single point connector. The
single point connector can comprise a bent metal piece 1205. The
single point connector (e.g., bent metal piece 1205) can be made of
any conductive metal, such as, for example, nickel, stainless
steel, copper-aluminum alloy, or of any other conductive material
described herein. In some cases, the ends of wires 1210 and 1215
are passed through holes in the bent metal piece and/or welded to
the bent metal piece. The wires can be any wire, including, but not
limited to, American Wire Gauge (AWG) 18 wires 1210 or AWG 10 wires
1215. In some cases, one or more wires (e.g., 1210) may be used to
sense voltage and therefore may be able to be thin (e.g., less than
about 2 mm in diameter, or AWG 18). In some cases, one or more
wires (e.g., 1215) may be thicker (e.g., greater than about 2 mm in
diameter, or AWG 18 gauge) and may be used to carry current to and
from the cell or cell module (e.g., as required for cell
balancing). The sensing line(s) (e.g., 1210) may be provided
separately from the current flow line(s) (e.g., 1215). In some
cases, first ends of the current carrying wires and the voltage
sense wire may be connected to a single point connector that is
connected to the cells or a busbar, while the other (second) ends
of the wires are separately connected to the battery management
system (e.g., the voltage sense wire is connected to a voltage
input port on the battery management system and the current wires
are connected to a single point connector which is connected to a
current input/output port on the battery management system). This
arrangement may enable voltage drop across the current flow lines
to be separated from the operational characteristics sensed by the
sensing lines. As previously described, the sensing and current
flow paths may be in electronic communication with the battery
management system.
[0203] Various interconnection configurations described herein in
relation to individual cells or a given group of cells may equally
apply to other groups of cells (or portions thereof) at least in
some configurations. In one example, interconnections such as, for
example, brazed positive and negative current collectors of cells,
braze enhanced by differences in coefficients of thermal expansion,
connecting (e.g., welding) cell bodies or features in cell bodies,
etc., may apply to (or be adapted to) groups of cells such as, for
example, packs, trays, towers, etc. In another example,
interconnections such as, for example, stamped pocketed
electrically conductive housing in cells and/or modules, etc., may
apply to (or be adapted to) groups of cells such as, for example,
towers, packs, etc. In yet another example, interconnections such
as, for example, busbars/interconnects between packs, etc., may in
some cases apply to (or be adapted to) groups of cells such as, for
example, cores, trays, etc. Further, stress-relieving
configurations (e.g., current transfer plates between cells,
spacers, spiral relief or compliance features/structures/patterns,
etc.) and electrical/structural features (e.g., single point
connectors, end-caps, etc.) may in some cases be applied to (or be
adapted to) any group of cells herein. The various interconnection
configurations may be applied at group level or to individual
cells. Thus, in an example, a spacer used between cells may be
configured for use as a spacer between packs or trays, a current
transfer plate between cells may be configured for use between
modules, a busbar on a pack may be configured for use as a busbar
on a tray, an interconnection interface comprising a feature on a
cell body for connecting cell bodies within a module may be
configured for connecting cell bodies of outer cells on adjacent
packs, and so on. Further, interconnections described in relation
to forming a series connection may be in some cases be adapted to
forming a parallel connection, and vice versa.
[0204] Devices, systems and methods of the present disclosure may
be combined with or modified by other devices, systems and/or
methods, such as, for example, those described in U.S. Pat. No.
3,663,295 ("STORAGE BATTERY ELECTROLYTE"), U.S. Pat. No. 3,775,181
("LITHIUM STORAGE CELLS WITH A FUSED ELECTROLYTE"), U.S. Pat. No.
8,268,471 ("HIGH-AMPERAGE ENERGY STORAGE DEVICE WITH LIQUID METAL
NEGATIVE ELECTRODE AND METHODS"), U.S. Patent Publication No.
2011/0014503 ("ALKALINE EARTH METAL ION BATTERY"), U.S. Patent
Publication No. 2011/0014505 ("LIQUID ELECTRODE BATTERY"), U.S.
Patent Publication No. 2012/0104990 ("ALKALI METAL ION BATTERY WITH
BIMETALLIC ELECTRODE"), and U.S. Patent Publication No.
2014/0099522 ("LOW-TEMPERATURE LIQUID METAL BATTERIES FOR
GRID-SCALED STORAGE"), each of which is entirely incorporated
herein by reference.
[0205] Energy storage devices of the disclosure may be used in
grid-scale settings or stand-alone settings. Energy storage device
of the disclosure can, in some cases, be used to power vehicles,
such as scooters, motorcycles, cars, trucks, trains, helicopters,
airplanes, and other mechanical devices, such as robots.
[0206] A person of skill in the art will recognize that battery
housing components may be constructed from materials other than the
examples provided herein. One or more of the electrically
conductive battery housing components, for example, may be
constructed from metals other than steel and/or from one or more
electrically conductive composites. The present disclosure
therefore is not limited to any particular battery housing
materials.
[0207] Any aspects of the disclosure described in relation to
cathodes can equally apply to anodes at least in some
configurations. Similarly, one or more battery electrodes and/or
the electrolyte may not be liquid in alternative configurations. In
an example, the electrolyte can be a polymer or a gel. In a further
example, at least one battery electrode can be a solid or a gel.
Furthermore, in some examples, the electrodes and/or electrolyte
may not include metal. Aspects of the disclosure are applicable to
a variety of energy storage/transformation devices without being
limited to liquid metal batteries.
[0208] It is to be understood that the terminology used herein is
used for the purpose of describing specific embodiments, and is not
intended to limit the scope of the present invention. It should be
noted that as used herein, the singular forms of "a", "an" and
"the" include plural references unless the context clearly dictates
otherwise. In addition, unless defined otherwise, all technical and
scientific terms used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs.
[0209] It should be understood from the foregoing that, while
particular implementations have been illustrated and described,
various modifications can be made thereto and are contemplated
herein. It is also not intended that the invention be limited by
the specific examples provided within the specification. While the
invention has been described with reference to the aforementioned
specification, the descriptions and illustrations of the preferable
embodiments herein are not meant to be construed in a limiting
sense. Furthermore, it shall be understood that all aspects of the
invention are not limited to the specific depictions,
configurations or relative proportions set forth herein which
depend upon a variety of conditions and variables. Various
modifications in form and detail of the embodiments of the
invention will be apparent to a person skilled in the art. It is
therefore contemplated that the invention shall also cover any such
modifications, variations and equivalents. It is intended that the
following claims define the scope of the invention and that methods
and structures within the scope of these claims and their
equivalents be covered thereby.
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